research on serial killers brain

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Scientists studied the brains of more than 800 prisoners. Here’s what they found.

Brain scans of incarcerated men reveal reduced gray matter in homicide offenders.

The brains of murderers look different from those of people convicted of other crimes—differences that could be linked to how they process empathy and morality.

Examining brain scans of more than 800 incarcerated men, new research co-authored by a leading University of Chicago neuroscientist found that individuals who had committed or attempted homicide had reduced gray matter when compared to those involved in other offenses. Those reductions were especially apparent in regions of the brain associated with emotional processing, behavioral control and social cognition.

“More gray matter means more cells, neurons and glia,” said Jean Decety , the Irving B. Harris Distinguished Service Professor in Psychology and Psychiatry at UChicago, noting differences in the orbitofrontal cortex and anterior temporal lobes of the brain. “That’s what you need to make computations, to process information—whether it’s emotional information that you use to feel empathy for someone else, or information that you use to control your behavior, to suppress your tendencies to react.”

A pioneering scholar in the cognitive neuroscience of moral reasoning and social decision-making, Decety’s research has focused both on psychopathy and on childhood moral development. The innovative study is a result of his longtime collaboration with University of New Mexico neuroscientist Kent Kiehl, who helps direct the nonprofit Mind Research Network .

“This work represents more than 10 years of data collection across eight prisons in two states,” Kiehl said. “We are fortunate to present the world’s largest sample of its kind and the results are quite remarkable.”

Published in the journal Brain Imaging and Behavior , the new study relied on structural MRI scans of the brains of men incarcerated in New Mexico and Wisconsin, which the researchers had obtained through previous studies.

Participants were divided into three groups: 203 individuals who were convicted of or self-reported a homicide or homicide attempt; 475 individuals who had committed aggravated battery/assault, armed robbery or other violent crimes; and 130 individuals involved in non-violent or minimally violent crimes.

Researchers excluded from the homicide group those who had been convicted as accomplices, as well as those whose criminal files or court records indicated a strong possibility of accidental death.

Although previous neuroimaging studies also have examined brains of murderers, this is the first research that uses such a large sample and that controls for factors like psychosis—excluding individuals who suffered brain injuries or psychiatric disorders such as schizophrenia.

In addition to Decety and Kiehl, other researchers on the study include first author Ashly Sajous-Turner, a University of New Mexico post-baccalaureate scholar; and Michael Koenigs of the University of Wisconsin.

However, the scholars note that they do not have enough evidence to draw a causal relationship between reduced gray matter and homicide. Ongoing research by Kiehl and Decety is following up a large sample of ultra high-risk boys—now in their mid-20s—to determine if the brain regions identified in this sample are predictive of future homicidal behavior. This work, the scholars feel, would help determine whether or not the results are causal.

Citation: “Aberrant brain gray matter in murderers,” Sajous-Turner et al., Brain Imaging and Behavior , July 5, 2019. DOI: 10.1007/s11682-019-00155-y

Funding: National Institute of Mental Health, Macarthur Foundation Law and Neuroscience Project

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What can neuroscience tell us about the mind of a serial killer?

Serial killers—people who repeatedly murder others—provoke revulsion but also a certain amount of fascination in the general public. But what can modern psychology and neuroscience tell us about what might be going on inside the head of such individuals?

Serial killers characteristically lack empathy for others, coupled with an apparent absence of guilt about their actions. At the same time, many can be superficially charming, allowing them to lure potential victims into their web of destruction. One explanation for such cognitive dissonance is that serial killers are individuals in whom two minds co-exist—one a rational self, able to successfully navigate the intricacies of acceptable social behaviour and even charm and seduce, the other a far more sinister self, capable of the most unspeakable and violent acts against others. This view has been a powerful stimulus in fictional portrayals ranging from Dr Jekyll and Mr Hyde , to Hitchcock’s Psycho , and a more recent film, Split . Yet there is little evidence that real-life serial killers suffer from dissociative identity disorder (DID), in which an individual has two or more personalities cohabiting in their mind, apparently unaware of each other.

Instead, DID is a condition more associated with victims, rather than perpetrators, of abuse, who adopt multiple personalities as a way of coming to terms with the horrors they have encountered. Of course a perpetrator of abuse may also be a victim, and many serial killers were abused as children, but in general they appear not to be split personalities, but rather people conscious of their acts. Despite this, there is surely a dichotomy in the minds of such individuals perhaps best personified by US killer Ted Bundy, who was a “charming, handsome, successful individual [yet also] a sadist, necrophile, rapist, and murderer with zero remorse who took pride in his ability to successfully kill and evade capture.”

“a recent brain imaging study … showed that criminal psychopaths had decreased connectivity between … a brain region that processes negative stimuli and those that give rise to fearful reactions”

One puzzling aspect of serial killers’ minds is the fact that they appear to lack—or can override—the emotional responses that in other people allows us to identify the pain and suffering of other humans as similar to our own, and empathise with that suffering. A possible explanation of this deficit was identified in a recent brain imaging study. This showed that criminal psychopaths had decreased connectivity between the amygdala—a brain region that processes negative stimuli and those that give rise to fearful reactions—and the prefrontal cortex, which interprets responses from the amygdala. When connectivity between these two regions is low, processing of negative stimuli in the amygdala does not translate into any strongly felt negative emotions. This may explain why criminal psychopaths do not feel guilty about their actions, or sad when their victims suffer.

Yet serial killers also seem to possess an enhanced emotional drive that leads to an urge to hurt and kill other human beings. This apparent contradiction in emotional responses still needs to be explained at a neurological level. At the same time, we should not ignore social influences as important factors in the development of such contradictory impulses. It seems possible that serial killers have somehow learned to view their victims as purely an object to be abused, or even an assembly of unconnected parts. This might explain why some killers have sex with dead victims, or even turn their bodies into objects of utility or decoration, but it does not explain why they seem so driven to hurt and kill their victims. One explanation for the latter phenomenon is that many serial killers are insecure individuals who feel compelled to kill due to a morbid fear of rejection. In many cases, the fear of rejection seems to result from having been abandoned or abused by a parent. Such fear may compel a fledgling serial killer to want to eliminate any objects of their affections. They may come to believe that by destroying the person they desire, they can eliminate the possibility of being abandoned, humiliated, or otherwise hurt, as they were in childhood.

Serial killers also appear to lack a sense of social conscience. Through our parents, siblings, teachers, peers, and other individuals who influence us as we grow up, we learn to distinguish right from wrong. It is this that inhibits us from engaging in anti-social behaviour. Yet serial killers seem to feel they are exempt from the most important social sanction of all—not taking another person’s life. For instance, Richard Ramirez, named the “Night Stalker” by the media, claimed at his trial that “you don’t understand me. You are not expected to. You are not capable of it. I am beyond your experience. I am beyond good and evil … I don’t believe in the hypocritical, moralistic dogma of this so-called civilized society.”

It remains far from clear why a few people react to abuse or trauma at an earlier stage in their lives by later becoming a serial killer. But hopefully new insights into the psychological or neurological basis of their actions may in the future help us to identify potential future such killers and dissuade them from committing such horrendous crimes.

Featured image via Pixabay

John Parrington is an Associate Professor in Molecular and Cellular Pharmacology at the University of Oxford, and a Tutorial Fellow in Medicine at Worcester College, Oxford. His latest book, Mind Shift (OUP, 2021), draws on the latest research on the human brain to show how it differs strikingly from those of other animals in its structure and function at a molecular and cellular level.

Parrington is also the author of The Deeper Genome (OUP, 2015) and Redesigning Life (OUP, 2016). He has published over 100 peer-reviewed articles in science journals including Nature, Current Biology, Journal of Cell Biology, Journal of Clinical Investigation, The EMBO Journal, Development, Developmental Biology , and Human Reproduction .

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7 Lessons from Murderers’ Brain Scans

February 1, 2021

On Wednesday, May 20, 1998, 15-year-old Kip Kinkel was caught with a stolen gun in his locker and suspended from school, pending possible expulsion. Police booked him on criminal charges and sent him home with his parents. According to Kip’s confession, his father was sitting at the kitchen counter drinking coffee while Kip grabbed a .22 rifle from his room then fired a bullet into the back of his dad’s head. When his mother arrived home later that day, Kip met her in the garage, told her he loved her, then shot her multiple times.

The next morning, dressed in a long trench coat, Kip drove his mom’s Ford Explorer to a spot near Thurston High School and parked it. Carrying a rifle and two handguns, Kip walked down a hallway and into the school cafeteria, firing off over 50 rounds that killed two students and wounded about two dozen others. A group of classmates, including one teenager who had been shot in the chest, finally subdued him.

After he was arrested and taken to the police station, the freckle-faced teenager lunged at an officer with a knife that he had strapped to his leg, yelling, “Kill me, shoot me.” The officer stepped back and used pepper spray on him. Kip was sentenced to 112 years in prison for aggravated murder and was prosecuted as an adult. Under Oregon law he was too young to face the death penalty. Kip had once been voted as “most likely to start World War III,” according to a Thurston High School student. Before the shootings, students at the high school said that Kip had talked about shooting people. After the shootings, officials found 5 bombs at the Kinkel residence, one of which went off when it was being disarmed.

Authorities found a note in the living room that Kip wrote, saying: “My head just doesn’t work right. God damn these VOICES inside my head… I have to kill people. I don’t know why… I have no other choice.”

What drives some people to kill another human being? Or to gun down dozens of their schoolmates? America has been captivated by killers for centuries—digging into their family histories, psychological profiles, and so much more. Now, thanks to brain SPECT imaging, we can also see inside their brains. What do brain scans reveal about murderers?

Amen Clinics, which has the world’s largest database of functional brain scans (over 160,0000 and growing), has scanned the brains of over 1,000 convicted felons, including over 100 murderers.

Here are 7 lessons from the brain scans of murderers.

1. people who do the worst things often have troubled brains..

The brains of murderers typically don’t look healthy. Brain SPECT imaging is a technology that measures blood flow and activity in the brain. It shows 3 things: areas with healthy activity, areas with too much activity, and areas with too little activity. On SPECT, the brains of murderers show abnormal activity in a variety of brain regions, especially the prefrontal cortex involved with empathy, judgment, and forethought. Look at this scan of a healthy brain compared to a scan from Kip Kinkel.

The healthy surface brain SPECT scan shows full, even, symmetrical activity.

Kip Kinkel’s surface brain SPECT scan shows several areas of low activity (the areas that look like holes indicate low blood flow).

2. Murder does not always look the same in the brain.

You might think there is a singular pattern in the brain of killers, but there isn’t. Look at the brain scans of two 15-year-old murderers, for example. They look very different. The brain scan of Kip Kinkel shows underlying damage and toxicity and is dramatically underactive. In the SPECT scan of Paul, a teen who murdered his mother and 8-year-old sister with a baseball bat, it is evident that his brain works too hard.

A healthy “active” scan shows the most active parts of the brain with blue representing the average activity and red (or sometimes red and white) representing the most active parts of the brain. In the healthy scan on the left, the most active area is in the cerebellum, at the back/bottom part of the brain.

Kip Kinkel’s active SPECT scan shows severe underactivity.

Paul’s active SPECT scan shows dramatic overactivity.

3. Traumatic brain injuries are a major cause of psychiatric illness and violence.

Few people know about the link between traumatic brain injuries (TBIs) and mental health problems because most psychiatrists never look at the brain. TBIs are associated with an increased risk of violent behavior, including suicide and murder. According to research in The Journal of Neuroscience , the rate of aggression and violence after a TBI ranges from 35%-90%. The brain scans of several of the murderers scanned at Amen Clinics show underlying damage to the brain from past head injuries.

4. Left temporal lobe abnormalities are common in violent people.

Many Amen Clinics patients who exhibited violence (murderers, arsonists, domestic assaults, rapists, bombers, etc.) had left temporal lobe abnormalities. The temporal lobes are located on either side of the brain behind the eyes and underneath the temples. Assault, murder, rape, arson, and other criminal behaviors are often associated with problems in this part of the brain. Other scientific research confirms that temporal lobe abnormalities are associated with increased aggression and violence.

5. Traditional mental health care is failing.

A number of our nation’s most notorious mass shooters—including Kip Kinkel (Springfield, OR, 1998), Eric Harris (Columbine, CO 1999), Seung-Hui Cho (Virginia Tech 2007), James Holmes (Aurora, CO, 2012), and Nikolas Cruz (Parkland, FL, 2018)—had seen psychiatrists or mental health professionals and had received “standard of care” treatment before their crimes.

The brain imaging work at Amen Clinics shows that cookie-cutter treatment plans for psychiatric illnesses don’t work. Not all brain types react the same way to psychotropic medications. For example, SSRIs, the most commonly prescribed antidepressants , are considered safe for many people. However, in some people with low activity in certain brain regions, they may increase impulsivity and behaviors that are out of character.

Scientific research, including a 2017 study in BMJ , has shown that some antidepressants increase the risk of violence, suicide, and homicide, and the FDA issues a black box warning for antidepressants for people up to the age of 24. A growing body of neuroimaging research, including a 2020 study in the International Journal of Molecular Sciences and a 2019 study in The American Journal of Psychiatry , shows that brain imaging may help predict which patients will respond favorably to antidepressants.

6. Murderous behavior based on brain problems can’t be fully excused.

Although brain dysfunction contributes to violence, it is not an excuse for bad behavior. People who commit heinous acts should not be excused and allowed to go home because they have a bad brain. Many people who have troubled brains never do anything bad. In judgment we must consider the brain. At this point in time, science shows that the brain is very important to moment-by-moment behavior, and it must be considered in sentencing people.

7. Brains can be rehabilitated.

What if our society evaluated and treated troubled brains, rather than simply warehousing them in toxic, stressful environments? Based on over 30 years at Amen Clinics of helping patients enhance their brain health and improve their lives, it’s clear that our society could potentially save tremendous amounts of money by making a significant percentage of these people more functional. With better brain health, violent criminals who get out of prison are more likely to be able to work, support themselves, and pay taxes. The Russian author Fyodor Dostoyevsky once said, “A society should be judged not by how it treats its outstanding citizens, but by how it treats its criminals.” Instead of just crime and punishment, SPECT imaging teaches us that we should also be thinking about crime, evaluation, and treatment.

Aggression, depression, anxiety, suicidal thoughts, and other mental health issues can’t wait. During these uncertain times, your mental well-being is more important than ever and waiting until life gets back to “normal” is likely to make your symptoms worsen over time.

At Amen Clinics, we’re here for you. We offer in-clinic brain scanning and appointments, as well as mental telehealth, remote clinical evaluations, and video therapy for adults, children, and couples. Find out more by speaking to a specialist today at 888-288-9834 or visit our contact page here .

34 Comments »

It has been said that the physical brain can be compared to a computer’s hardware, and the mind to its software. Defects in and damage to the hardware can most certainly affect the proper functioning of the software, but most problems are with the software itself.

In the case of healthy/normal vs. unhealthy/abnormal human behavior, it goes without saying that there are many other variables, including other physical elements such as genes, DNA, diet, exposure to toxins, etc.; and since a brain is not literally a machine, those elements can also affect the “hardware”.

Other factors in human thinking and behavior also include one’s basic individual “wiring” (personality), life experiences, education, etc.

The bottom line (for me) is that no one is fully responsible for all of their actions; nevertheless, of course, criminals must be stopped from repeating or continuing their harmful behavior.

Comment by Dolores Woodrum — February 5, 2021 @ 3:32 AM

Dr. Amen, My husband has multiple traumas and multiple traumatic brain injuries. He has severe, chronic PTSD, delayed onset, with dissociate symptoms. He has been really symptomatic since January 9, 2021. I don’t know how to help him. He runs away from me every day and every night. I barely see him since January 8. I don’t know if a SPECT Scan would help us or not. I want my husband to feel better, and I’m at a loss. Should he pursue ECT? TMS? More medications? Talk therapy? The talk therapy is exacerbating the symptoms. I want him to go voluntarily to a hospital here in the Phoenix, AZ area, but he is refusing. He is a veteran and some of the trauma is due to abuse at the hospital. Please help.

Comment by Angela Smalley — February 5, 2021 @ 4:08 AM

Your articles continue to sell what your clinics can read and the fact that your reads have been consistent with certain behaviors. What they are missing is what folks can do to support healthy brains. Unfortunately your services are very expensive and not affordable by the average citizen. Insurance doesn’t cover it. What can we do for the various afflictions you write about?

Comment by Bmmickey — February 5, 2021 @ 4:12 AM

My SPECT was very abnormal. Areas of extreme activity and underactivity. I couldn’t hurt a fly but I am emotionally labile. It takes more than a bad brain.

Comment by Kathy Weir — February 5, 2021 @ 5:09 AM

Thank you for this published insight. I was principal to a reform school for women. This was before i read your books. Dr David Hawkins was our attending psychiatrist at that time. He was an astute and valuable asset to myself and ALL my teachers. I do not know if hes still aroundas he was older than i, but your published research can fill any void in that respect. The world needs to know sooo much more about brains and their care and feeding. I thank God for you and your research!!!

Comment by Jo Ellard — February 5, 2021 @ 5:57 AM

I would like to see a brain scan/study on young men (18-29 yrs) from being in prison system. A medium “correctional” facility to be exact. Where the innocence of our young people are being compromised by older inmates AND lace of protection for correction officers.

Comment by Lisa Limoge — February 5, 2021 @ 6:00 AM

This is all good information, but the problem herein lies that there are, probably most that cannot afford this kind of treatment. I’ve been to your clinic and had scans but that’s all we could afford, it’s sad to get this kind of health care you have to be rich.

Comment by Brad Bear — February 5, 2021 @ 7:55 AM

What are you doing to help people who cannot afford your high prices? You keep giving us all of this information but what good is it if we can’t afford? I feel like you’re teasing us. You’re putting more stress on us knowing that there’s some help out there but we can’t reach it because we can’t afford it.

Comment by Barbara — February 5, 2021 @ 9:05 AM

I did a scan exactly a year ago at Amen clinic. , there were couple of scallops. I got prescribe vitamins. The insomnia that took me there have not improved. I believe I was under treated

Comment by Bernadette Uzo — February 5, 2021 @ 9:09 AM

Angela Smalley: If your husband is a Veteran you need to go where ever institution in this Country that takes care of them. Write letters to President Biden . Call to Wonded Worriors Foundation and ask for a group support. Do what ever you think can do. And most of all PRAY!!

Comment by Luz m zapata — February 5, 2021 @ 9:11 AM

I’m curious if the brain functioning or damage is common to all murderers. What about family killers like Scott Peterson or Chris Watts who tend to premeditate the murders? Are their brains damaged or are they just plain evil.

Comment by Patty Sullivan — February 5, 2021 @ 9:55 AM

I find it interesting that Buddhists and other spiritual belief systems teach that the mind is in the heart. While I find Dr. Amen’s information fascinating, I cannot help but think that the brain is a computer lacking human qualities that can only be balanced by integrating heartfelt information into the body. In addition to the critical thinking skills taught in higher education, we also need lessons in meditation to balance mind, body, and spirit for the sake of our sanity.

Comment by Susana — February 5, 2021 @ 5:36 PM

my husband is a marine corps gulf war veteran. recently he has been diagnosed with cptsd and severe depression. could all the vaccines and pills that were given before and during his deployments cause a TBI.

Comment by dee dee — February 5, 2021 @ 6:05 PM

i would like to have my own scanner so i could see my brain’s activity – could monitor it better – would love to watch change over time thank you very much for your info – as always!

Comment by penny waters — February 5, 2021 @ 9:02 PM

I am crying because my son and I need and want help and can not afford this. So sad he has to go to jail because their is no help! So sad! So wrong!

Comment by Bergey Heather — February 6, 2021 @ 2:47 AM

You don’t need a brain scan to know the number one indicator of violence:

Being a biological MALE!

Comment by Katherine Adelaide — February 6, 2021 @ 4:42 AM

Dear Angela, You are a wonderful caring wife who clearly loves her husband and is desperate for help. I just wanted you to know that someone across the country is thinking about and praying for you and your husband. I really hope he can get help. Too many good people are suffering.

Comment by Jen — February 6, 2021 @ 5:04 AM

Dr. I so wish I could go to your clinic. I cannot afford it. Doctors need to be trained from you so they can order spects and insurance pay. I have medicaid. Please help this. Love you and your wife

Comment by Nadia Martin — February 6, 2021 @ 5:36 AM

Angela, I’m a veteran with PTSD, TBI and resultant mental issues. I have friends with the same. Please don’t give up hope. There are ways to mitigate the things your husband is going through, and they aren’t necessarily expensive, nor what he will likely find at the VA. You are exactly correct in the result of talk therapy! I have experience (not medical advice) in other, easily available, less expensive, and not psychological ways that have helped me. And Badger Balm Stress Soother. Wonderful aromatherapy stuff. I use it for sleep and stress.

Any veteran can use the local ER system, and the VA will reimburse the hospital. Make sure to give the veterans information on check-in. Please don’t think you must rely on an appointment at the VA.

I’d like to encourage you in that it’s not your fault. You are not the enemy, nor the cause. If he has left the a/o, it could be because he’s protecting you from what he’s going through. Please give him the space and understanding. Understanding – or even the willingness to try – is critical. If you pray, now is a good time to ask Jesus for protection of your husband’s mind, his person, and his emotions. For some guidance in prayers that will help and not hurt, look up The Power of a Praying Wife.

There is a hotline for dealing with veterans issues. White House VA Hotline. (855) 948-2311. Stay on the line until you get a live person. If you don’t feel at ease with the person who answers the phone, simply tell them you’re having phone issues (I hate little white lies, but this one might be excusable) and call back. Hopefully you’ll get another person. It’s not connected with the VA – it’s to help you navigate their system, and for veterans who need someone to talk to. 24/7/365.

Above all, there is hope. Don’t give up.

N C Carlson, author Listed Alphabetically, The Prodigal Daughter

Comment by Nancy Carlson — February 6, 2021 @ 5:46 AM

I have a son who received a spect, (after fighting for it), frontal lobe-decreased blood flow…has had a multitude of doctors and walk away therapists….He is now 38…(just stated 2-3 years ago, “Mom, my siblings are going on with their families , i need my own life community quiet”.. Since then, in Maine we found him a home..with his dog ,and then the virus hit..and has been isolated for a year….YET-there is no TBI specialist-psych-therapists- etc….With everything this man has been through since 18…..Where is the help?…He is in Waldo county maine..any suggestions……Please..thankyou and God Bless all ….

Comment by JUDITH a warner — February 6, 2021 @ 5:52 AM

Angela Smalley, regarding your husband – I am in the care of two Amen Clinics doctors after SPECT scans revealed a TBI from multiple concussions, severe PTSD, a mood disorder that appears to be caused by injury to the area of mood regulation, and I have dissociative episodes. My symptoms left me mentally disabled in my 30’s. I am climbing my way out of that status through recovery with The Amen Clinics. Your husband may be a veteran, but the VA currently is not prepared to provide the level of physical improvement in your husband’s brain health that the Amen Clinics can and will if he follows their treatment for whatever his SPECT scans reveal. Please understand the importance of guided psychiatric care with use of SPECT scans. My mental health floundered dangerously while receiving standard psychiatric care for over two decades. In 2020, my mental functioning began improving within three months of the start of the Amen Clinics’ personalized treatment plan and continues to do so. My life is worth the $4000 scans. That is what it came down to. How much money is my quality of life worth? I wish your husband the best of care, and to you both I wish you less cause for concern. Much Respect – Leeann M.

Comment by Leeann M. — February 6, 2021 @ 6:36 AM

I feel like this starts at birth. Birth trauma can cause a lot of damage that affects the child well into adulthood. i would be fascinated to see what their birth and childhood history is . Similar to TBI. Being born blue at birth and having a cord wrapped around your neck – though ‘resolves quickly’ in the medical view – that trauma stays in the body and affects things. Any loss of O2 at birth or even other seemingly minor things like getting stuck in the birth canal, using forceps, vacuum suction – all affect the child and likely the brain.

Comment by Amanda — February 6, 2021 @ 7:00 AM

This is very interesting research. Hope you can do more of it.

Comment by B.j. — February 6, 2021 @ 7:21 AM

Would make common sense that an injured brain would bring about abnormal behavior.

Comment by Egidio Migioia — February 6, 2021 @ 9:17 AM

I’ve had what I’m told were probably three TIAs. It frightens me because at 77 all I really have to work with is my mind. I’ve had an MRI of my brain which shows minor damage in the past. When I was 13 I had a brain injury, the result of flying off my bicycle and landing on my head. I was unconscious for long enough that my brother thought I was dead. My parents did nothing fir me, though it was clear I’d had a concussion, terrible headache and double vision. Could this have damaged my brain enough to cause TIAs sixty four years later?

Comment by Dianne Faucher — February 6, 2021 @ 9:46 AM

Neurofeedback is a very potent technique for teaching the brain better self regulation skills. Applying it to the prison population has been done for decades, going back to the work of Doug Quirk in the 1970’s, dramatically reducing recidivism. Brain behavior, the basis for our external behaviors, can be altered! If you are struggling with unwanted behaviors, no matter what the cause, emotional trauma, TBI, etc. please find a neurofeedback practitioner in your area and train your brain to support your best intentions.

Comment by John Mekrut — February 6, 2021 @ 10:18 AM

I agree with Barbara’s comment Feb.5. It is frustrating to desire this kind of care, but it not be affordable. I wish insurance companies would get on board with new ideas and holistic therapy.

Comment by Erin — February 6, 2021 @ 6:33 PM

I love reading your books and articles, but the cost of your treatment facility is too high for most of us….. it’s sad, it hurts knowing there is help, but insurance company’s can not cover it…. and it will cause us into bankruptcy just to be healthy…

Comment by Tasha Hoon — February 7, 2021 @ 9:37 AM

Thank you, Daniel Amen and Team. This is such very important information and my hope is that eventually it moves into mainstream consideration as we continue to advance as a society and planet.

Comment by Lisa Boisvert — February 7, 2021 @ 8:08 PM

My 33 year old daughter had a SPECT Scan and evaluation two years ago, and was told that her previous diagnosis of Bi-polar Affective Disorder was incorrect, and she was actually displaying symptoms of high functioning Autism, and the correct diagnosis should be Asperger’s Syndrome. The attending psychiatrist at your clinic advised her to cut back, and eventually eliminate the medication she was taking for bi-polar disorder, and to increase an SSRI medication. Although we could see some of the symptoms that fit your psychiatrist’s diagnosis (and I do believe there is a “cluster” of symptoms that presently contribute to our daughter’s proper diagnosis), it was disastrous when she altered these medications. Bi-polar behaviors increased, along with some aggressive behaviors that she had not displayed previously. She has now discontinued the SSRI medication and is back on a medication for Bi-polar disorder, as prescribed by her local psychiatrist. I actually believe that your attending psychiatrist was projecting some of her own symptoms. I am a neurofeedback practitioner, and our daughter has benefited from sessions, as well. I believe that the work you do at Amen Clinic is of extreme importance, but I also feel that perhaps some of your psychiatrists’ work should be better peer reviewed, particularly of your younger, less experienced ones. Your attending psychiatrist ruled out Bi-polar disorder based on the fact that our daughter did not go for days without sleeping. Pretty much everyone in this field of work knows that there is more than one type of Bi-polar/mood disorder, and her assessment, I believe was incorrect. I am wondering if our daughter might have been given a completely different (or at least more comprehensive) diagnosis, had she seen a different psychiatrist at your clinic.

Comment by Margaret Arter — February 12, 2021 @ 8:27 AM

Hello Margaret, thank you for reaching out and informing us of your experience. Our Clinic Director at Amen Clinics Chicago would be happy to speak to you, please contact her at 224-804-9223.

Comment by Amen Clinics — February 15, 2021 @ 1:40 PM

If you cannot afford to pay for a scan or a clinic visit, you might find some relief in Dr. Amen’s book, Change Your Brain, Change Your Life. I bought a used paperback copy on Amazon. Contains tests that can tell you which remedies might help you. Some are very simple. Lots of tips for calming your mind.

Comment by Barbara — February 16, 2021 @ 2:23 PM

Interesting studies and ensuing discussion. I’m a 36 year old woman with moderate autism/Asperger Syndrome (which I wasn’t diagnosed with until age 29, in 2014; diagnosed previously with mild OCD and generalized anxiety as a teen). I always did well academically and love reading/researching things, but I’m not very good socially, or at managing frustration and very unexpected things. I did well at all grade levels in school, only to find employment very challenging. It’s easy for me to sit and learn patiently in a chair in a closed setting, like school, but not easy to adapt to all the social nuances and rapid pace of most lines of work. I’ve often wondered what my brain scans would show. I was born to an older mother (almost 43 years old at my birth), had umbilical cord wrapped around my neck, jaundice at birth. Older half sister suspected autism early, but I was too verbal, happy at home, and otherwise well adjusted for a diagnosis, especially back then in the 1980s and 1990s when only the more extreme, male, nonverbal forms of autism were understood. Hope to continue to learn more about the brain, human differences, and all the factors that affect us in this mysterious life.

Comment by Khendra Murdock — February 19, 2021 @ 2:35 PM

In the early 1990s my son was in my car when soeone approached and began to key the car. My son got out and said to the person, that he knew who the person and he had the license plate. This teacher backed over my son three times throwing him up in the air and down. At the hosptal he was told that there were hand injuries and possible knee injuries. Yes, his hand had to be split open surgically to relieve the injury and the knee surgeon had to tie the ligaments etc to the kn ee. Since that time my son’s personality has undergone difficult changes. He was still able to study at the University and get degrees in education, sociology, criminology and psychology. However he never regain the personality that he had before the incidenet. I woud be interested in reading appropriate writings by Dr. Amen. I saw him on Fox News after the incidents in Texas and was impressed. My degrees were in psychology /sociology . I have 2 masters degrees and I did my doctoral studies in criminology in education, studying teachers . Thank you for any articles/books that you can suggest.

Comment by Dr. Rosemary ONeill-McNeil — May 29, 2022 @ 11:43 AM

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Murderous Minds: Can We See the Mark of Cain?

Some of our debates seem eternal, like the frozen ﬁgures on a Grecian urn. Point: Criminals must be held responsible for their crimes; we want no excuses, no sob stories. Counterpoint: Our behavior is shaped by complex, often overpowering factors; let our understanding temper our vengeance. What happens to these positions when technology enables us, for the ﬁrst time in history, to look into the brain of the murderer and compare its activity with that of a brain like our own?

Adrian Raine, D.Phil., a leading researcher on the biosocial bases of violent behavior, used positron emission tomography (PET) in the ﬁrst brain-imaging study of the brains of murderers. Comparing their brains with those of a matched group of normal individuals, and exploiting PET technology’s ability to measure differences in function in many brain areas, he asked questions that philosophers, theologians, and legal theorists have pondered for centuries.

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Blame it on Cain. Please don’t blame it on me. Oh, its nobody’s fault, but when you need somebody to burn, blame it on Cain. —Elvis Costello and The Attractions

I f you could literally look into the mind of a murderer, what would you see? Would the activity of Jeffrey Dahmer’s brain look like yours or mine? Would his brain be much less active? More active? And how would the brain activation proﬁle of serial killers like Dahmer differ from those of less memorable, but more common, single killers? Not long ago, answers to questions like these were the province of pulp ﬁction or space-age movies. Now advances in brain imaging are giving us far more than a glimpse into the mind of the murderer. Although studies are in their infancy, they not only provide a base for future research into violence and aggression but raise provocative, important questions about free will, blame, and punishment.

22 Murderers: The First Look

In the ﬁrst published brain-imaging study of murderers, 1 my colleagues and I scanned the brains of 22 murderers who had pleaded not guilty by reason of insanity, or had been judged incompetent to stand trial. We compared them with the brains of 22 non-murderers matching the murderers in sex and age. The scanning technique we used was positron emission tomography (PET), a method pioneered in psychiatry by Monte Buchsbaum. This enabled us to measure the metabolic activity of different regions of the brain, including the prefrontal cortex (which sits above the eyes and immediately behind the forehead).

Let me brieﬂy describe our method. In PET, ﬁrst a cyclotron makes a short-lived radioactive isotope, ﬂuorine-18 (its short half-life holds down the dose of radiation to the subject). The isotope is then “tagged,” or mixed, with an analogue of glucose-2deoxyglucose. The resulting compound is injected into the subject right after he begins a cognitive task that “challenges” or activates the part of the brain one suspects may be dysfunctional. In this case, we used the “continuous performance task,” a standard visual task known to activate the frontal region of the brain, since we hypothesized that poor functioning of the prefrontal region might be particularly involved in predisposing to violence. In this task, numbers from 0 to 9 are ﬂashed on a screen at the rate of one per second, with subjects pressing a button every time they see “0.” This goes on for 32 minutes and, believe me, it is a very boring task. It requires the subject to maintain focused attention and mental vigilance for a sustained period. The prefrontal region of the brain is responsible, in part, for this vigilance.

While subjects were performing the task, we took a series of blood samples from them to measure glucose and deoxyglucose. Because glucose is the only source of energy used by the brain, the radioactive ﬂuorine isotope is quickly carried to the brain, where the most active regions receive the largest quantities in order to meet their high energy needs. By the end of the 32-minute cognitive task, the radioactivity is “ﬁxed” in the subject’s brain.

The subject was then taken to the PET scanner. In this procedure, crystals positioned around the head detect gamma photon rays that are emitted by the isotope, while a computer maps the origin of the emitted rays. Because more rays are emitted by brain regions that are more active (and absorbed more radioactive glucose), the activity levels of different brain regions can be picked up by the scan. And because radioactivity is mostly “ﬁxed” in place by the end of the cognitive task, the measurements during scanning are of the levels of activity at the time of the earlier task—not afterward when the subject is in the scanner.

A Predisposition to Violence

What did the study reveal? The key ﬁnding is illustrated in the images above, which show the brain scan of a normal individual used as a control (left) and the brain scan of a murderer (right) who had impulsively killed his victim.

The striking difference is at the top of the images. The normal subject, on the left, shows much activation, while the murderer, on the right, shows little. As we had hypothesized, the area showing the difference is the prefrontal cortex. At the bottom of each scan, however, you can see that the occipital cortex is activated about equally in the normal person and in the murderer. (This brain area is activated because the task was visual.) Thus the deﬁcit in the murderers was selective. We found no deﬁcit in the temporal region and, as is indicated in the illustration, the occipital cortex was at least as well activated in the murderer as in the control.

What does this mean? We think that poorer functioning of the prefrontal cortex predisposes an individual to violence in several ways:

Note that although there are many associations between poor prefrontal function and violence, brain dysfunction may create only a predisposition to violence, which environmental, psychological, and social factors may enhance or diminish.

Going Deeper

We took our imaging research another step by increasing our sample from 22 to 41 murderers, and also by increasing our control group to 41. This larger sample gave us more statistical power to detect group differences. In 1997, we reported our updated ﬁndings, 2 which, ﬁrst of all, conﬁrmed the signiﬁcant reduction in prefrontal activity in murderers.

We found that the brain structure known as the left angular gyrus functioned more poorly in the murderers. The angular gyrus lies at the junction of the temporal, parietal, and occipital regions of the brain, integrating information from the three lobes. Diminished activation in the left angular gyrus has been correlated with reduced verbal ability , 3 while damage to this region has been linked to deﬁcits in reading and arithmetic. Such cognitive deﬁcits could predispose to educational and occupational failure, in turn predisposing to crime and violence. (One interesting conﬁrmation of this interpretation is that learning deﬁcits are unusually common in violent offenders.)

We found reduced functioning of the corpus callosum, the band of white nerve ﬁbers that allows communication between the left and the right cerebral hemispheres. We speculate that poor connection between hemispheres may mean that the right hemisphere, which is involved in the generation of negative emotion, 4 may be less well regulated and controlled by the inhibitory processes of the more dominant left hemisphere. This may contribute to how and whether violence is expressed. Interestingly, rats stressed early in life are right-hemisphere-dominant for mouse killing. 5 Severing the corpus callosum in these rats results in an increase in mouse killing, 6 indicating that the left hemisphere normally acts to inhibit the right hemisphere’s mouse-killing tendency. Furthermore, researchers have observed inappropriate emotional expression and inability to grasp long-term implications in human split-brain patients (who have had their corpus callosum surgically severed). This suggests that such emotional expression by violent offenders, and their lack of long-term planning, may result in part from poor functioning of the corpus callosum. Callosal dysfunction, though unlikely to cause aggression, may contribute to violence in those with other limbic and cortical abnormalities.

We observed unusual functioning in subcortical regions, including the amygdala, hippocampus, and thalamus. Murderers tended to show relatively lower activation of these structures in the left hemisphere but higher activation in the right hemisphere. Interpretations of these ﬁndings are speculative, but it is not surprising that these structures function abnormally in murderers. The amygdala has been repeatedly associated with aggressive behavior in both animals and humans. 7 As part of the neural network that underlies the processing of socially relevant information, its disruption could explain the anti-social behavior of some violent people and the misappraisal of ambiguous stimuli in social situations that have potential for violent encounters. 8

The amygdala, hippocampus, and prefrontal cortex are involved in governing emotion; together with the thalamus, they are critical to learning, memory, and attention. Their abnormal functioning may contribute to the failure to learn from experience that characterizes criminal and violent offenders. 9 Also, the amygdala seems to mediate the experience of fear in animals, and autonomic arousal in humans. Abnormalities in the amygdala could accord with the fearlessness theory of violence, since offenders have been found to have reduced autonomic arousal. 10

Fact or Artifact

Could all of these ﬁndings have been produced by some difference between the murders and controls other than the factor of violence? We think not. Although six of the murderers were schizophrenic, we controlled for that by including six nonviolent schizophrenics in the matched normal group. Nor did group differences in brain functioning correlate with differences in age, sex, handedness, history of head injury, medications, or illegal drug use.

Could the scans of the murderers have revealed poorer prefrontal functioning because the murderers could not do the continuous performance task? We checked this; their performance was almost identical to that of the controls. But this parity in performance on a challenge task raises still another question. How could the murderers do as well as the controls if the murderers had a dysfunction in the part of the brain critical to performing the task? The answer, we think, lies in the occipital cortex, which was more activated in murderers than in controls. The murderers seem to have recruited this visual brain area into vigorous action to help them to perform the visual task, thus compensating for their poor prefrontal functioning.

We believe this study is the ﬁrst evidence from brain imaging that the brains of a large sample of murderers are functionally different from those of normal people. Prefrontal deﬁcits have also been found in schizophrenia and depression, but those studies have never revealed our speciﬁc pattern of ﬁndings involving the prefrontal cortex, corpus callosum, angular gyrus, amygdala, hippocampus, and thalamus. This suggests a unique PET “signature” of the brains of some murderers.

What were the limitations of our study? For one thing, our sample was highly selective, consisting of murderers pleading not guilty by reason of insanity—an unusual subgroup of violent offenders, but one important in forensic psychiatry. We do not yet know if violent offenders in the community who commit serious but nonlethal violent acts also have prefrontal dysfunction, nor have we established causality. It is possible, for example, that prefrontal dysfunction does not cause violence; instead, living a violent life (including substance abuse and ﬁghts) may cause the brain dysfunction we observed. No previous study, however, has shown that substance abuse and head injuries produce the speciﬁc proﬁle of brain deﬁcits that we observed. Finally, although we controlled for schizophrenia, other psychiatric disorders in the control group could have contributed to the ﬁndings. But again, this speciﬁc pattern of brain deﬁcits has never been reported in any psychiatric group.

If brain deﬁcits directly contribute to violence, what causes the deﬁcits? What are the roles of environment and genetics? Although we controlled for a history of head injury, more subtle injuries early in life could contribute to brain dysfunction in the murderers. For example, we know that violent offenders are more likely to have grown up in abusive homes. If a baby is repeatedly and roughly shaken, the white ﬁbers that link the prefrontal cortex with other brain structures can be lacerated, effectively cutting off the rest of the brain from prefrontal regulatory control. Could early infant abuse have contributed to prefrontal deﬁcits in the murderers? Drug and alcohol abuse may also contribute. Conversely, the real culprit may be genetics. Although deﬁnitive studies have not been conducted, there could be a heritable basis to prefrontal functioning. Behavioral and molecular genetic studies increasingly suggest that crime and violence are rooted in genetics.

In Cold Blood

Newspapers regularly refer to the “cold-blooded” predator who kills with little or no emotion. Such a criminal is contrasted with the passionate, hotheaded individual who kills in a moment of unbridled emotion. Is the predatory killer more controlled and regulated in his brain functioning, and is the murderer who kills in a moment of passion—the “affective” murderer—lacking in brain regulation and control? Animal research has established that different neural pathways underlie predatory aggression and affective or defensive aggression. Now imaging research in humans is beginning to suggest the same thing, at least with respect to homicide.

With Reid Melloy, a forensic expert from the University of California, San Diego, we developed a way to divide our murderers into either “predatory” or “affective.” 11 The predatory murderers were regulated and controlled, were lacking in emotional affect, were more likely to attack strangers, and tended to plan their murders. In contrast, the affective murderers showed much less planning. Their acts were more likely to occur in the home and be driven by a high degree of emotion. Although some murderers could not be assigned with conﬁdence to either category, we were able to assign 15 of the 41 murderers to the predatory group and 9 to the affective group.

Our study found that affective murderers lacked the prefrontal functioning that can control aggressive impulses. Conversely, the regulated, controlled, predatory killers showed relatively good prefrontal functioning; an intact prefrontal cortex seemed to enable them to regulate their behavior for nefarious ends. This does not explain, however, why the predatory murderer is murderous in the ﬁrst place. Does the explanation lie submerged in subcortical structures? Both groups of murderers had higher functioning of the right subcortex (deﬁned as the midbrain, amygdala, hippocampus, and thalamus) than did controls. We speculate that this excessive subcortical activity may predispose to an aggressive temperament in both groups; but while those in the predatory group have sufﬁciently good prefrontal functioning to regulate their aggressive impulses (bullying and manipulating others to achieve their desired goals), affectively violent individuals lack prefrontal modulatory control, resulting in more impulsive, dysregulated, aggressive outbursts.

Good and Bad Homes

On Tuesday, March 24, 1998, Andrew Golden (age 11) and Mitchell Johnson (age 13) killed 5 and wounded 10 of their schoolmates in the heartland of America. A year earlier, Jeremy Strohmeyer, a high-school student from Long Beach, California, killed a seven-year-old girl in a restroom in Nevada. In many cases, murderers come from backgrounds of neglect, abuse, or poverty (“bad homes”), and it is easy to point an accusing ﬁnger at these possible causes of violence. But the young killers in these two cases came from “good homes” that, although not perfect, were not typical of the homes of those who now share their prison cells. In these cases, is the real culprit not poor family functioning but poor brain functioning?

We tested this hypothesis by dividing our sample of murderers into those from relatively good home backgrounds and those from relatively bad homes. 12 To do so, we took into account early physical abuse, sexual abuse, neglect, extreme poverty, foster home placement, having a criminal parent, severe family conﬂict, and divorce. On this basis, we identiﬁed 12 murderers as having experienced signiﬁcant psychosocial deprivation; we viewed 26 as having experienced minimal deprivation.

The results are in the illustration above, which shows the scan of a normal control (left), a murderer from a bad home (middle), and a murderer from a relatively good home (right). The odd man out is the murderer from the good home. While the deprived murderer shows relatively good prefrontal functioning, the non-deprived murderer shows the characteristic lack of prefrontal functioning. We found that murderers from good homes had a 14.2 percent reduction in functioning of their right orbitofrontal cortex. This brain area is of particular interest. When previously well-controlled adults suffer damage to the orbitofrontal cortex, they begin to display personality and emotional deﬁcits that parallel criminal psychopathic behavior, or what Antonio Damasio and colleagues term “acquired sociopathy.” 13

At ﬁrst, these ﬁndings seemed unexpected, but from another perspective they made sense. If a seriously violent offender comes from a bad home, it is plausible to seek the causes of his violence there. If he comes from a good home, however, environmental causes seem less plausible. Biological deﬁcits become a more likely explanation. Consistent with our ﬁndings through brain imaging, previous research has shown that lack of a normally developed sense of fear in schoolchildren is more often coupled with antisocial behavior if the child comes from a good home environment. 10 That is, the biological deﬁcit (poor development of fear) is found in those who display antisocial behavior but lack a social predisposition to it. Not surprisingly, the right orbitofrontal cortex seems important in fear conditioning.

How “Free Is Our Will?

What are the social implications of these brain-imaging studies? Do all of us have freedom of will in the strict sense?

Many theologians, philosophers, and even scientists would argue that, barring exceptional circumstances (such as severe mental illness), we each have full control over our actions. Theologians, for example, suggest that we can elect to let God into our souls, choose whether or not to commit sin, and must therefore accept that criminal actions (or sins) are products of a will under our full control. Other scientists and philosophers eschew the idea of a disembodied soul with a free will. Francis Crick, for example, believes that free will is nothing more than a large assembly of neurons and that it would be possible to build a machine that would believe it had free will. 14 Perhaps we are nothing more than gene machines that mislead ourselves into believing we have choices in life.

I argue for a middle ground. Some people have almost complete freedom of will in their actions; others have relatively little. Instead of viewing “intent” in all-or-nothing terms as (with few exceptions) does the law, I see a continuum. Early social, biological, and genetic developments play substantial roles. For some, freedom of will is constrained early in life by forces beyond their control.

When people speak of free will, they point to our overriding sense of having the power to choose at this instant: to drink from a glass or drop this issue of Cerebrum . Surely this demonstrates free will? But take a different example. We know that alcoholism is a disease with a substantial genetic component. If we seat an alcoholic and a nonalcoholic in front of a glass of beer, then yes, in an absolute sense they can choose whether or not to drink it. But we also know that the probability is that the alcoholic will be less able to resist drinking. In this situation, his free will is constrained by genetic, biological, and environmental forces beyond his control. Probably we will never be able fully to predict behavior, but we can predict it to some extent and that suggests constraints on freedom of will. Decisions made by a computer’s hardware are produced by its software program and decisions that our brains make in speciﬁc situations are products of our unique genetic coding and early life experiences.

If brain deﬁcits make a person more likely to commit violent crime, and if the cause of the brain deﬁcits was not under that person’s control, then should he be held fully responsible for his crimes? Suppose that a baby (we’ll call him Elvis) is born in difﬁcult labor to a mother who used drugs and alcohol during pregnancy. This prenatal and perinatal trauma causes the infant to be born with some brain damage, which is made worse by the father’s vigorously shaking the baby during his bouts of non-stop crying. The baby’s whiplash injury leads to disconnection of the prefrontal cortex from the rest of the brain, disengaging the emergency brake on impulsive, aggressive behavior. The impulsiveness and lack of reﬂection induced by the brain dysfunction lead the growing child to be more likely to fall out of trees, be hit by cars, and thereby suffer further head injury that leads to more brain damage. The brain damage renders the adult Elvis less likely to be able to control his aggressive feelings, so that one day he shoots a friend in a ﬁt of temper. In his panic, leaving the scene of the crime, he shoots a passerby who attempts to intervene, killing him also. A PET brain scan reveals substantially poorer functioning of the prefrontal cortex and the corpus callosum in Elvis.

Should we execute him? We strongly suspect that brain damage made him much more likely to commit violent acts. We ascertain that the causes of the damage were early in life and beyond his control. Of course, we have to protect society, and unless we can treat this brain dysfunction we may need to keep Elvis in secure conditions for the rest of his life, but does he deserve to lose his life, given the demonstrable constraints on his free will?

In debating this issue at a conference on Neuroscience and the Human Spirit in Washington, DC, in September 1998, one scientist responded to this scenario by arguing that if a person has risk factors he has to take responsibility for them. Like a person at risk for seizures who decides not to drive a car, the person at risk for violence must take steps to ensure that he does not harm others. He is still responsible, still has freedom of will.

This is good, practical sense for some people. But there is a problem with this argument for executing Elvis. Responsibility and self-reﬂection are not disembodied, ethereal processes; they are rooted in the brain. Patients with a damaged ventromedial prefrontal cortex (a part of the brain above the middle of the eyes) are known to become irresponsible, lacking in self-discipline, and unable to consider the consequences of their actions. The very mechanism that supports the ability to take responsibility is damaged in Elvis. He may no longer be able to reﬂect on his behavior or take responsibility for his risky predispositions.

Most prisoners I have met who are suspected of brain dysfunction have no idea that anything is wrong with them. Often they grew up with this problem; it has always been part of them. Even when this is pointed out to them, they believe (like much of the general public) that the causes of their violence lie in poverty, unemployment, bad inﬂuences, and (sometimes, but not always), poor parenting and child abuse. They are shocked and disbelieving if I tell them that brain dysfunction and biology contribute to violence. Poverty and bad parenting, after all, can be seen and recognized; biological factors are invisible and intangible. So it is not just that the brain mechanisms underlying responsibility are damaged in the violent offender, preventing him from acting to rectify the causes of his violence. Even if he could reﬂect on himself, he probably would end up accusing the wrong risk factors.

Blaming It on Cain

Cooped up at home at Christmas time, we get on top of each other. Herbert Weinstein was no exception. In 1991, by the end of the Christmas holidays, he had had about as much as he could take of his wife in their twelfth-ﬂoor Manhattan apartment. After strangling her, he threw her out of the window to make her death look like suicide. He was charged with second-degree murder. Things looked bad for Weinstein until his defense lawyer had his brain scanned and found poor functioning caused by a cyst in the left frontal and temporal brain regions. The prosecution tried to have the PET evidence ruled inadmissible but after an extensive hearing, the judge admitted it. This was apparently the ﬁrst time that PET data had been admitted as evidence for an insanity defense during a trial itself.

Before this ruling, PET had been strictly limited to the sentencing hearing, when all possible grounds for mitigation may be introduced. In Weinstein’s case, the PET data proved compelling. In a plea-bargain arrangement, the charge against him was reduced to manslaughter, yielding a much lighter sentence. 15

In cases like Herbert Weinstein’s, the mark of Cain may literally be on the brain. But blaming Cain is unpopular. At a scientiﬁc level it is hard to know whether brain dysfunction caused the violent behavior or whether living a violent life resulted in the brain damage. Studying the brain basis of violence is in its infancy. Even if other scientists reproduce and extend our ﬁndings, there will be the difﬁculty of going from ﬁndings based on groups of offenders in research studies to conclusions about an individual killer.

Biological research on violence is politically unpopular with both right and left. Conservatives worry that biological research will be used to let vicious offenders off the hook. Liberals fret that brain-scan technology may someday be used preventively to lock up an innocent person with the proﬁle of a violent offender.

I suspect, though, that these are not the main reasons for opposition to applying biological ﬁndings on violence to legal cases. Behind the opposition are multiple political, theological, legal, and moral issues. 10 Biological research on violence is politically unpopular with both right and left. Conservatives worry that biological research will be used to let vicious offenders off the hook. Liberals fret that brain-scan technology may someday be used preventively to lock up an innocent person with the proﬁle of a violent offender. Theologians dislike the idea that biology constrains individual freedom of will because they believe that God made us equally able to embrace good and reject sin. Legally, we are guilty of a crime if we have criminal intent and know that what we are doing is wrong; and even violent offenders with substantial brain damage can tell the difference between right and wrong, know that they are doing wrong, and sometimes carefully plan their actions. In doing so, they show criminal intent and demonstrate legal sanity. At the broadest moral level, most of us feel that offenders have to be punished if they do wrong; not to punish would be morally wrong. In addition, practically, what would happen if society excused serious crimes because of bad brains? Could this not become a license to kill?

Against this broad opposition, will brain-imaging research on violence ever make a difference? I think that it could and should make a difference; but because it profoundly challenges our way of conceptualizing crime (not to mention our “gut reaction” to crime, a reaction perhaps rooted in our evolution as a species), I am far from certain that it will make a difference. We have much to lose if it does not. Let me elaborate.

The political, legal, and moral questions raised by this research are complex and worrisome, but they are too important to ignore. The question that law courts ask when dealing with a defendant is “did he do it”? There are obvious reasons for this question. But the more important question—one that courts rarely ask—is “Why did he do it?”

Violent crime may still be with us because we have largely ignored that question. Continuing to ignore it may ensure that we remain vulnerable to violence. In part, prevention programs have failed to stop violence because they systematically ignored the biological part of the biosocial equation that explains violence.

The violent offender is like a jigsaw puzzle. Decades of careful psychosocial research have identiﬁed some of the pieces (e.g., child abuse, poverty, poor parental supervision, delinquent peers, and gangs). Recently we have begun to identify the biological pieces (e.g., low physiological arousal, high testosterone, birth complications, and low serotonin). Now brain-imaging research is beginning to identify the brain mechanisms (involving the prefrontal cortex, amygdala, hippocampus, and corpus callosum). The challenge is to uncover more neurobiological pieces and put them together with the social pieces to ﬁll out our picture of the violent offender.

Some thinkers see a strong sociobiological basis for homicide, violence, and property crimes. 10,16 In evolutionary terms, it has paid some individuals to be antisocial, parasites on the rest of us, and to seize others’ resources to increase their own genetic ﬁtness as measured by producing more offspring. Perhaps this gave rise to a genetic predisposition to crime and aggression. 10 But I would argue that evolutionary forces also built into all of us (including antisocials) strong emotional reactions against criminals: vengeance, hate, retribution, and a desire to ostracize. These leave little room for understanding and forgiveness. Whether or not there is a genetic or a biological predisposition to violence, when a violent crime is committed, we want to blame someone. We want someone to pay. Evolution seems to have forged not only crime and violence but our armor against any evidence that might “excuse” them.

Brain-imaging research on violence troubles us by challenging the way we think about crime. It questions our treatment of murderers in the way that, looking back 200 years, we question the shackling of the mentally ill. The history of civilization suggests that, at least over the long term, society has tended to become more humane. Two hundred years from now will we have reconceptualized recidivistic, serious criminal behavior as a clinical disorder with roots in early social, biological, and genetic forces beyond the individual’s control? Will we look back aghast at the execution of seriously violent offenders? Will we view execution of prisoners as we now view the burning of witches?

I would like to think so, but our gut reaction to crime may never change. A key reason for our success as a species is our effective mechanism for shutting out those in our midst with the mark of Cain. In the end, that mechanism may block all change in how we think about and deal with crime.

I believe such a refusal to change would be an enormous mistake. When we learned to control our environment, the human race was freed from the yoke of the evolutionary forces that once shaped us. Now we can think and act more freely, and use the scientiﬁc knowledge base we are acquiring. What was an adaptive response to violent crime 100,000 years ago is no longer so adaptive. Our time-immemorial practices do protect society from particular criminals, but they do nothing to prevent the next generation of violence.

Brain-imaging research is beginning to give us new insights into what makes a violent offender. These early ﬁndings may at least lead us to rethink our approach to violence and goad us into obtaining new answers to the causes and cures of crime while we continue to protect society.

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Aberrant brain gray matter in murderers

A. sajous-turner.

1 The Mind Research Network, Albuquerque, NM

2 University of New Mexico, Albuquerque, NM

N.E. Anderson

P. nyalakanti, k. harenski, c. harenski.

3 University of Wisconsin – Madison, Madison, WI

4 University of Chicago, Chicago, IL

Associated Data

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Homicide is a significant societal problem with economic costs in the billions of dollars annually and incalculable emotional impact on victims and society. Despite this high burden, we know very little about the neuroscience of individuals who commit homicide. Here we examine brain gray matter differences in incarcerated adult males who have committed homicide (n=203) compared to other non-homicide offenders (n = 605; total n = 808). Homicide offenders’ show reduced gray matter in brain areas critical for behavioral control and social cognition compared with subsets of other violent and non-violent offenders. This demonstrates, for the first time, that unique brain abnormalities may distinguish offenders who kill from other serious violent offenders and non-violent antisocial individuals.

Introduction

Interpersonal violence is a significant societal problem, and homicide, in particular, stands out among violent acts for its severe and absolute consequences. More than 17,000 people are murdered each year in the United States ( U.S. Department of Justice: Federal Bureau of Investigation, 2016 ) and estimates suggest the average cost per murder surpasses $17 million, including costs to victims, court proceedings, law enforcement, and loss of productivity. This sums to a staggering $255 billion dollar economic burden annually in the United States alone ( DeLisi et al., 2010 ). These estimates, of course, cannot account for social and emotional consequences cast around the victims, relatives, and the rest of society. The gravity and prevalence of these costs, combined with increasing understanding of the complex bio-psychosocial influences on behavior, has fostered a perspective of viewing violence and homicide as a major public health concern, and has thus motivated the examination of individual differences that promote and protect individuals from these outcomes ( Reidy et al., 2015 ).

Despite longstanding scientific interest, and its great impact on society, we still have limited knowledge of the neuroscience related to homicidal behavior. Examining the biological underpinnings of violence and homicide has become an increasingly tractable challenge encouraged by advancing technology in neuroscience, genetics, and related sciences. Modern brain imaging methods have provided a foundation for understanding pathophysiology and developmental factors that may contribute to violent behavior. A large and growing body of research highlights the roles of frontal, temporal, limbic, and paralimbic brain circuits for promoting and regulating aggression, antisocial behavior, and disinhibited behavior more generally. This work has provided some insight into the deficits exhibited by individuals with a propensity for even the most extreme violence ( Bannon, Salis, & O’Leary, 2015 ; Rosell & Siever, 2015 ; Smith, Smith, & Misquitta, 2016 ).

Some of the earliest functional neuroimaging studies that examined homicide offenders concluded that murderers were characterized by reduced activity in brain areas including lateral and medial prefrontal cortex ( Raine, Buchsbaum, & LaCasse, 1997 ; Raine et al., 1994 ; Raine et al., 1998 ), as well as medial temporal regions, including the amygdala, and extended temporal and parietal regions ( Raine et al., 1997 ; Raine et al., 1998 ). These early studies relied on murderers who had been found not guilty by reason of insanity (NGRI), and thus include effects of comorbid psychosis and organic brain injury alongside those effects specifically related to homicidal behavior. In the same vein, more recent work still commonly comingles homicidal behavior with other psychiatric conditions, e.g., schizophrenia, or with violent antisocial behavior more generally, e.g. ( Amen, Hanks, Prunella, & Green, 2007 ; Lam et al., 2017 ; Puri et al., 2008 ; Raine, Lencz, Bihrle, LaCasse, & Colletti, 2000 ; Yang et al., 2010 ). These studies still highlight the role of frontal and temporo-limbic brain areas, but they are not sufficient to discriminate homicide from other violent outcomes or from other psychiatric disorders per se. Further, the degree to which these same brain structures may be useful in distinguishing between homicidal behavior and less severe forms of violence or antisocial behavior is less certain, as control groups are ordinarily comprised of non-incarcerated subjects. One recent study from our team reported that incarcerated adolescent boys who had committed homicide showed reduced gray matter in medial and lateral anterior temporal lobe and insula, relative to other serious offenders ( Cope et al., 2014 ). Still, no prior study, to our knowledge, has compared the brains of adult homicide offenders directly with other violent offenders who have not committed a homicide. We hypothesize that homicide offenders will have deficits in areas of executive functioning and limbic control areas within the prefrontal cortex and anterior temporal cortex compared to non-homicide offenders.

Materials and Methods

Experimental design.

Here we sought to examine differences in brain structure between adult male inmates who have committed a homicide offense and those who did not. We used archival data from prior NIH-supported studies (see Acknowledgments ) that included structural MRI data and pertinent assessment data. Participants were separated into one of three groups: homicide offenders, violent offenders who have not committed a homicide, and non-violent/minimally violent offenders. Voxel based morphometric (VBM) analyses were conducted to compare brain differences between groups.

Participants

We included incarcerated adult male participants from New Mexico and Wisconsin prisons who had undergone a structural MRI scan in one of our research studies using a 12 channel T1-weighted multi-echo sequence. The total sample included 998 incarcerated adult males with T1 (MPRAGE) scans. A number of participants were excluded due to abnormal radiology reports n = 10; Traumatic brain injury with loss of consciousness greater than 2 hours n = 43; n = 5 were excluded due to their crime being too ambiguous to classify, n = 50 were excluded to the diagnosis of a psychotic disorder and n = 82 participants were excluded due to the inability to estimate the amount of time they had been incarcerated (a covariate in our models), thus, a total n = 190 participants were excluded from this omnibus sample. The final study sample included brain data from n = 808 incarcerated male adults.

Participants were categorized into three groups; Homicide, Violent non-homicide, and Non-violent/minimally violent. The “Homicide group” (n = 203) included men who were convicted of a homicide offense (n = 81); self-reported committing a homicide offense (n = 72); indicated during confidential research interviews a serious attempt to commit a homicide (n = 32) but failed or outcome was unknown; or were convicted of committing an attempted murder offense (n = 18). A report of a “serious attempt of homicide” included an explicit admission of attempting to commit a homicide offense during a confidential interview. Some participants were charged with a homicide offense under felony murder statutes (i.e., NM Stat § 30-2-1 (1996 through 1st Sess 50th Legis) . These statutes refer to accomplices or co-conspirators of a dangerous crime i.e., armed robbery, home invasion, drug dealers, getaway drivers, etc., who are charged with murder even though they were not the ones who committed the actual homicide. These participants were not included in the Homicide category. Also, homicide offenders who’s criminal file information indicated there was a strong possibility of the crime actually being an accidental death or that they were not directly involved in the homicide offense were excluded from the ‘Homicide group’. These measures were taken to try and ensure all members of the ‘Homicide group’ were the perpetrators of a confirmed homicide/attempted homicide.

The “Violent Non-Homicide group” (n = 475) included individuals who had charges such as aggravated battery/robbery/assault, any crimes involving serious physical contact with a victim, armed robbery, domestic violence that included a weapon or great bodily harm, and kidnapping/unlawful confinement, arson (if there was a victim who endured physical harm), and reckless injury with weapons enhancement. Any criminal conviction with the enhancement of a deadly weapon or great bodily harm where there was physical contact between the participant and a victim (not an accidental or reckless car accident) were included. Participants who self-reported committing a violent crime such as; armed robbery; aggravated assault/battery, rape/sexual assault (child or adult) were categorized as violent. In the event that the participant had a charge of a violent offense but through further investigation through their file revealed that they did not have physical contact with a victim or intentional contact with the victim (ex. Aggravated battery due to a reckless driving incident or armed robbery due to theft of a weapon during a robbery in which they did not come into contact with the victims) with the absence of other violent charges and no self-reported violent crimes, they were considered minimally violent.

“Minimally Violent Group” (n = 130) included those inmates with charges for, or self-reporting less than 3 simple assault/battery/domestics (no weapon enhancements or serious injury), driving while under the influence (DUI/DWI), drug possession or trafficking, prostitution, weapons possession or trafficking, arson of an uninhabited dwelling or property (with no victim), child abuse/neglect (unless intentional physical harm came to the child), reckless driving, voyeurism, possession of child pornography, pimping/trafficking, unlawful confinement/kidnapping (if there was no physical contact with a victim), resisting arrest, battery upon a peace officer, theft, forgery, burglary, fraud, driving offenses, escape, failure to appear, vandalism, and property damage. In the event that a participant was convicted of a violent crime, but according to their criminal file did not have physical contact with a victim they were included as minimally violent. Offenders who committed vehicular homicide while under the influence or due to reckless driving such as speeding, or running a stop sign, or participants who were charged with felony homicide but did not actually commit the index offense, who also did not have any other violent convictions or self-reports, were included in this group. Participants, who did not self-report committing any violent crimes (as defined in the Violent Non-homicide group description) and did not have any criminal charges for a violent offense, were also considered non-violent/minimally-violent.

All information for New Mexico participants were gathered using information from participant’s official criminal files from which we used arrest data, incarceration history such as movement data, parole data, conviction history, disciplinary reports, good time reports, police reports, victim impact statements, participant statements and letters, as well as public court records and self-reported criminal history during confidential interviews. For Wisconsin participants we used court records as well as public institutional information from the Wisconsin correctional department’s inmate lookup website which provided information about incarceration history through their movement records and convictions history. For all participants we also used public newspapers and court documents such as appeals to corroborate institutional information and gain more information about the circumstances of a crime such as if others were involved, possible motivations for the crime or any other relevant history or circumstances. Participant interviews such as for scoring psychopathy were used as well to determine level of violence or to gain more insight into the circumstances surrounding any crimes committed.

Participants were excluded for abnormal radiology reports, e.g. having white matter lesions, large cysts, etc. Participants were also excluded if their crime was too ambiguous to adequately categorize. The present study reports from a final sample of n = 808 incarcerated adult male offenders. This research was approved by multiple IRBs, including the Ethical and Independent Review Services (E&I), the University of Wisconsin-Madison, divisions of the Corrections Department of Wisconsin and The New Mexico Corrections Department as well as the Office of Human Research Protections (OHRP). All individuals volunteered to participate after providing written informed consent. Participation did not affect institutional status (e.g., security level, privileges, and parole or release date) and participants were paid for their time at a rate commensurate with pay for work assignments at their facility.

Assessments

Psychopathy.

All offenders were assessed for psychopathy using the Psychopathy Checklist-Revised (PCL-R; ( Hare, 2003 ). The PCL-R is an expert-rated semi-structured interview that assesses the presence of 20 traits and behavioral patterns that may be evident across the lifespan (e.g., shallow affect, callousness, lack of guilt or remorse, juvenile delinquency, poor behavioral controls, and impulsive/antisocial behaviors). These 20 items are scored on a three-point scale (0, 1, and 2) indicating no-evidence, some evidence, and pervasive evidence. Scores range from 0 to 40 and the accepted diagnostic cutoff for psychopathy is 30 and above; however, these scores are also commonly used on a continuous scale ( Hare & Neumann, 2005 ) and PCL-R total scores were used for all analysis.

Substance Use Severity

Substance use severity was quantified as the total months of substance use derived from a modified survey based on the Addiction Severity Index ( McLellan et al., 1992 ), ASI-X. Scores were divided by age (at the time of MRI scan) to account for opportunity for use, and square root transformed to correct for skew.

Intelligence

IQ estimates were calculated using the vocabulary and matrix reasoning subtests of the Wechsler Adult Intelligence Scale III (WAIS-III) ( Wechsler, 1997 ), a stable estimate of IQ ( Ryan, Lopez, & Werth, 1999 ).

Psychiatric Disorders

From the Structured Clinical Interview for DSM –IV Axis I and II Disorders (SCID-I; SCID-II) ( First, Spitzer, Gibbon, & Williams, 2002 ) offenders were assessed for mood, anxiety, psychotic and personality disorders. Offenders with a history of psychosis or psychotic disorders were excluded from the analyses.

Other Assessments

Trained researchers administered a post-head injury symptoms questionnaire to evaluate history of traumatic brain injury (TBI) ( King, Crawford, Wenden, Moss, & Wade, 1995 ). Participants were excluded if they had a traumatic brain injury resulting in loss of consciousness for longer than two hours or had MRI findings indicative of brain injury by radiological review.

Time in Prison

Time spent in prison estimates were gathered using participant’s movement record or self-reported data from their institutional records and PCL-R interviews. Time in prison was divided by age and square root transformed to address skewness (see Table 1 ).

Comparison of covariates across groups of incarcerated offenders

Note: Significant group differences indicated by ANOVA are followed up by t-test comparisons between groups. Substance Use is quantified as a severity measure based on how many months the individual engaged in regular (3+ times/week) substance use, divided by age to account for opportunity for use. Total brain volume is a combination of total gray matter + white matter. Time in prison is calculated as approximate months in prison and divided by age.

MRI Acquisition

High-resolution T1-weighted structural MRI scans were acquired on the Mind Research Network Siemens 1.5T Avanto mobile scanner, stationed at one of the eight prisons in this study, using a multi-echo MPRAGE pulse sequence kindly provided by Massachusetts General Hospital Radiology Department (repetition time = 2530 ms, echo times = 1.64 ms, 3.50 ms, 5.36 ms, 7.22 ms, inversion time = 1100 ms, flip angle = 7°, slice thickness = 1.3 mm, matrix size = 256 × 256) yielding 128 sagittal slices with an in-plane resolution of 1.0 mm × 1.0 mm. Data were pre-processed and analyzed using Statistical Parametric Mapping software (SPM12; Wellcome Department of Cognitive Neurology, London, UK; http://www.fil.ion.ucl.ac.uk/spm ). T1 images were manually inspected by an operator blind to subject identity and realigned to ensure proper spatial normalization.

Images were spatially normalized to the SPM12 T1 Montreal Neurological Institute (MNI) template using non-linear registration, segmented into gray matter, white matter, and cerebrospinal fluid, and modulated with the Jacobian determinants to preserve total volume ( Ashburner & Friston, 2000 ). Finally, the images were resampled to 1.5 × 1.5 × 1.5 mm and smoothed with a 10 mm full-width at half-maximum (FWHM) Gaussian kernel. Voxels with a gray matter value of < .15 were excluded in order to remove possible edge effects between gray matter and white matter.

Whole brain analysis

One way ANOVA was performed on a voxel-by-voxel basis over the whole brain using SPM12 to evaluate differences in regional gray matter volumes between Homicide (n = 203), Violent Non-Homicide (n = 475) and Minimally Violent (n=130) offenders, with all three groups included as factors in each analysis. The ANOVA model included each subject’s total brain volume (i.e., gray matter plus white matter), PCL-R total scores, substance use severity, age at time of scan, IQ, and time in prison variables as covariates. Whole brain analyses using the False Discovery Rate for control over Type I error, were performed for all comparisons. Results from comparisons between homicide offenders and violent non-homicide offenders are presented in Figure 1 , Figure 3 and Table 2 . Results from comparisons between homicide offenders and all non-homicide offenders are presented in Figure 2 .

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Areas where homicide offenders exhibit reduced gray matter density compared to other violent offenders are highlighted in blue/green. The color scale represents t-values for the comparison at each voxel in the brain with a p < .05 threshold corrected for the expected false-discovery rate across the whole brain. A selection of anatomical labels and corresponding statistical values and coordinates are given in Table 1 .

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Areas where homicide offenders exhibit reduced gray matter density compared to non-homicide offenders are highlighted in blue/green. The color scale represents t-values for the comparison at each voxel in the brain with a p < .05 threshold corrected for the expected false-discovery rate across the whole brain.

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This figure shows a single generic brain in axial slices. Areas where homicide offenders exhibit reduced gray matter density compared to other violent offenders are highlighted in blue/green. The color scale represents t-values for the comparison at each voxel in the brain with a p < .05 threshold corrected for the expected false-discovery rate across the whole brain. A selection of anatomical labels and corresponding statistical values and coordinates are given in Table 1 .

Coordinates and Labels for selected Violent Non-Homicide versus Homicide group effects.

Data Availability

Homicide offenders (n = 203) showed robust deficits in ventromedial/orbitofrontal cortex, anterior temporal cortex, ventrolateral and dorsolateral prefrontal cortex, dorsomedial prefrontal cortex, insula, cerebellum, dorsal anterior cingulate, mid-cingulate, and posterior cingulate cortex extending into the precuneus and superior parietal regions compared to all offenders who have not committed a homicide offense (n = 605) (see Figure 2 ). These results remained stable when comparing the homicide group against other severely violent offenders (n = 475) (see Figure 1 ; Figure 3 ; Table 2 ). Effects here were not attributable to age, IQ, psychopathy, substance use severity, or time in prison, which were entered as covariates in all analyses along with total gray and white matter to control for global differences in brain size (see Table 1 ). Comparisons between the violent (no-homicide) and minimally-violent offenders yielded mostly null results, and no results survived correction for multiple comparisons.

Supplemental Analysis

Following recommendations from review, and due to potential interest in alternative categorization strategies, we examined gray matter differences between additional subcategories of our primary groups. These analyses compared convicted homicide offenders versus self-report homicide offenders and attempted homicide offenders vs. completed homicide offenders, including parsing self-reported attempted homicide and convicted attempted homicide. No significant differences in gray matter were found between these subgroups, in any regions highlighted in our primary analysis here. These supplementary analyses further justify our initial categorization strategy of considering these groups together as homicide offenders. These analyses are provided in more detail supplementary material (S1) .

This study examined gray matter differences among incarcerated male offenders comparing those who have committed a homicide and those who have not. We report widespread reductions in gray matter affecting brain regions involved in emotional processing, behavioral control, executive function, and social cognition. These results were stable when comparing against both subcategories of violent and minimally violent groups. Comparisons between the violent (non-homicide) and non-violent groups yielded mostly null results, suggesting that major individual differences distinguish those who committed homicide, and that the brains of ordinary violent offenders do not differ much, structurally, from minimally violent and antisocial inmates.

The reductions in gray matter among homicide offenders were evident in a number of brain areas important for affective processing, social cognition, and strategic behavioral control. Prominently featured in these results are the orbitofrontal/ventromedial prefrontal cortex, the anterior temporal cortex, insula, medial prefrontal/anterior cingulate and precuneus/posterior cingulate cortex. For example, the abilities to assess the cognitive perspective and emotional states of others is often described as theory of mind (ToM) and empathy, and these abilities are important for effective social-cognitive function and adaptive social behavior. Prior neuroimaging studies suggest important roles for the orbitofrontal cortex, medial prefrontal cortex, temporal poles, insula, and anterior cingulate cortex in tasks that require assessment of others’ cognitive states and feelings ( Decety, 2011 ; Olson, Plotzker, & Ezzyat, 2007 ; Vollm et al., 2006 ). Partially overlapping with these circuits, brain networks involved in regulating one’s own emotional states draw on ventromedial, ventrolateral, dorsomedial, and dorsolateral prefrontal cortex under varied conditions of appraisal and control ( Hutcherson, Plassmann, Gross, & Rangel, 2012 ; Ochsner, Silvers, & Buhle, 2012 ). The orbitofrontal cortex has been identified for its role in planning/executing behavior based on expected outcomes ( Howard, Gottfried, Tobler, & Kahnt, 2015 ; Rich & Wallis, 2016 ) experiencing regret over one’s behavior ( Camille et al., 2004 ; Coricelli et al., 2005 ), and effective moral decision-making ( Moll, de Oliveira-Souza, Bramati, & Grafman, 2002 ). These frontal regions exert influence on primary emotional regions such as the amygdala, sensory areas, and parietal integration areas. Further, the anterior cingulate and insula have been described for their combined role in redistributing cognitive resources effectively during executive control and other forms of directed cognitive appraisal ( Bush, Luu, & Posner, 2000 ; Ochsner & Gross, 2005 ; Ochsner et al., 2012 ). By considering first the roles of larger functional networks, it follows that limitations in some individual, specific brain regions may affect a number of varied functional properties of the brain affecting behavior.

Reduced gray matter in many of these same brain regions have been previously implicated in studies comparing violent and/or homicide offenders characterized with other neurological and psychiatric issues with healthy controls e.g. ( Amen et al., 2007 ; Lam et al., 2017 ; Raine et al., 1997 ; Raine et al., 2000 ; Raine et al., 1998 ). The present findings also expand the network of brain areas previously identified in youth who had committed homicide – namely anterior-medial and lateral temporal lobes, and the insula ( Cope et al., 2014 ). These findings also align with prior work that has related similar brain abnormalities with aggressive behavior ( Rosell & Siever, 2015 ), and more general impairments in behavioral control and decision-making; for instance, among those with persistent antisocial behavior ( Raine et al., 2000 ) and youth with conduct disorder ( Fairchild et al., 2011 ). Further, these regions overlap with many paralimbic regions related to psychopathic traits ( Anderson & Kiehl, 2012 ; Ermer, Cope, Nyalakanti, Calhoun, & Kiehl, 2012 , 2013 ; Gregory et al., 2012 ). Psychopathic traits remain among the best predictors of future violence in released offenders ( Hare, Clark, Grann, & Thornton, 2000 ; Salekin, Rogers, & Sewell, 1996 ). Continuing research should therefore consider how brain imaging data may reveal the pathophysiological and developmental origins of psychopathic traits, and how these may combine with social and environmental factors to predict violent outcomes, particularly homicide.

In the context of this growing literature, it should be recognized that the localized deficits in gray matter exhibited in this sample of homicide offenders are not necessarily specific to homicidal behavior. Instead, these patterns may indicate impairment across a wide range of emotion and cognitive systems that together reduce essential checks and balances in executive function, moral judgement, and behavioral controls. The evident discriminability of homicide offenders in this sample based on gray matter may therefore be one of degree, demonstrating reliable separation in line with the severity of these effects.

Limitations and Future Directions

Our study included a number of control measures for possible moderating variables, such as psychopathy, IQ, age, and time in prison. However, it is possible that homicide offenders differ from violent offenders in other constructs without psychometric coverage. For example, there may be dimensions of impulsivity that were not captured by our assessments that may differ between groups (i.e., homicide offenders may be more impulsive than non-homicide offenders, on average). We address a common limitation of research examining homicide that relies only on official conviction data. This introduces limitations of the criminal justice system, policing biases, and sentencing strategies (e.g. plea bargains) which add noise to models intended to hone in on specific offenses. By combing our best resources including official convictions, court-records, and by including self-reported incidents, we have intended to capture more precise groupings. Comparisons provided in supplementary materials reinforce the merits of this strategy, though it comes with its own limitations and likely remains imperfect.

In an attempt to limit variability attributable to external factors and gross neurological abnormalities, we have excluded individuals with major head injuries and significant radiological findings. While it is not our intention to limit all variability contributing to abnormal brain structure, this choice reflects a motivation to focus on individual differences not directly attributable to injury or other acute neurological events. We fully intend to focus future efforts on examining these relationships directly, as brain injuries represent a major influence on neurological function and behavior. We hope this initial work leads to more research in this area and more granular parcellation of constructs relevant to homicidal behavior in particular.

These results may also have important implications for the criminal justice system. Indeed, brain imaging data is increasingly being used in court ( Farahany, 2016 ; Gaudet & Marchant, 2016 ). While this report demonstrates aggregate differences between homicide offenders and other violent offenders that are highly statistically significant, this should not be mistaken for the ability to identify individual homicide offenders using brain data alone, nor should this work be interpreted as predicting future homicidal behavior. This study does include a very large sample but we nevertheless recommend continued efforts for replication and extension. Additionally, as previous work comparing violent individuals to community samples have shown violent offenders have some enhanced brain regions compared to community controls ( De Brito et al., 2009 ; Tiihonen et al., 2008 ), this current study does not include a comparison sample of community members. Given the heterogeneity and complexity of homicide behavior, contrasting an incarcerated individual to a member of the community may introduce additional confounding factors related to effects of socioeconomic status, incarceration, policing and sentencing and a multitude of other environmental and biological factors. The description of abnormal neural networks among homicide offenders is a key step in furthering our understanding of the connection between biology and serious violent behavior. As such, this work represents an incremental step in making our society safer by demonstrating the crucial role of brain health and development in the most extreme forms of violence represented among antisocial populations.

Supplementary Material

11682_2019_155_moesm1_esm, acknowledgments:.

The authors would like to thank the Wisconsin Department of Corrections and the New Mexico Department of Corrections for their cooperative efforts with the Mind Research Network.

Funding: This research was supported in part by grants from the National Institute of Mental Health: R01DA026505, R01DA026964, R01DA020870, R01MH070539, and R01MH087525 (PI: Kent Kiehl), R01MH087525 (PI: Jean Decety), R01MH090169 (PI: David Kosson) and the Macarthur Foundation Law and Neuroscience Project.

Publisher's Disclaimer: This Author Accepted Manuscript is a PDF file of a an unedited peer-reviewed manuscript that has been accepted for publication but has not been copyedited or corrected. The official version of record that is published in the journal is kept up to date and so may therefore differ from this version.

Conflict of Interest: The authors report no competing interests.

Ethical Approval: This research was approved by multiple IRBs, including the Ethical and Independent Review Services (E&I), the University of Wisconsin-Madison, divisions of the Corrections Department of Wisconsin and The New Mexico Corrections Department as well as the Office of Human Research Protections (OHRP).

Informed Consent: All individuals volunteered to participate after providing written informed consent. Participation did not affect institutional status (e.g., security level, privileges, and parole or release date) and participants were paid for their time at a rate commensurate with pay for work assignments at their facility.

Data and materials availability: All processed data (completely de-identified), code, and materials used will be made available to any scientist seeking to replicate or re-analyze the data.

Can Genes And Brain Abnormalities Create Killers?

Breakthroughs in neuroscience are changing the way criminals are defended in court. Scientific research on brain scans and DNA has provided new insight on how some kinds of criminals are different from law-abiding citizens. Differences in their brains and genes may predispose them to violence.

Barbara Bradley Hagerty, correspondent, NPR's national desk Stephen Morse, professor of psychology and law in psychiatry, University of Pennsylvania Joshua Greene, assistant professor, Harvard University Kent Kiehl, director of Mobile Imaging Core and Clinical Cognitive Neuroscience at the University of New Mexico

Check Out The NPR Series

NEAL CONAN, host:

This is TALK OF THE NATION. Im Neal Conan in Washington.

Today, the criminal brain and what's being called neurolaw. Scientific research on brain scans and DNA provide new insight on what makes some kinds of criminals different than you and me, information that's begun to be introduced as evidence in some trials.

The data challenge how we think about right and wrong, about guilt and innocent and about the penalty to fit the crime.

NPR's Barbara Bradley Hagerty just completed a three-part series for NPR on this topic. If you missed the broadcasts on MORNING EDITION, you can find a link to them on our website, and she joins us in just a moment.

Later in the hour, what makes a psychopath, and does neuroscience tell us that once a psychopath, always a psychopath? But first, we want to hear from those of you who have questions about this new research and its implications.

We're going to focus a little bit later in the program, on how it's being introduced as evidence in courts of law, so if you've dealt with criminals as lawyers or in law enforcement, if you've come in contact with neurolaw, give us a call, 800-989-8255. Email us, [email protected] You can also join the conversation at that aforementioned website. Go to npr.org. Click on TALK OF THE NATION.

NPR's Barbara Bradley Hagerty joins us here in Studio 3A. Barbara, always nice to have you on the program.

BARBARA BRADLEY HAGERTY: Thanks so much, Neal.

CONAN: Now, you got interested in the subject through a neuroscientist named James Fallon at UC Irvine.

HAGERTY: That's right, that's right. Jim Fallon has studied the brains of serial killers for something like 20 years, and he had a theory about what makes a serial killer's brain different from yours and mine. And his theory basically involves a couple of things, three things, but two of them is brain function and genes.

So he believes that the brains of serial killers operate differently. On brain scans, it looks like their orbital frontal cortex, which is right above the eyes, is a little bit less active, or a lot less active, than the amygdale, when they're processing information.

He and others believe that the orbital frontal cortex is involved with moral decision-making and ethical behavior, and it...

CONAN: Executive decisions.

HAGERTY: Right, exactly. And it puts a brake on the amygdale, which is involved with fear, and anger, and violence, and appetites and that kind of thing.

CONAN: The reptile brain.

HAGERTY: That's exactly right. So if the orbital cortex, the moral decision-making area of the brain, is not doing its job, then he believes that this person is more likely to be violent. So it's a break the brakes aren't working, essentially.

CONAN: And the genetic component of this?

HAGERTY: Yeah, that's really interesting, too. There are certain genes that have been found to be related to violence, and one in particular that's gotten a lot of attention is called the MAOA gene. It's also called the warrior gene because it regulates the serotonin system in the brain - serotonin in the brain, which affects moods, you know, think Prozac, that kind of thing.

Fallon and others have found that if you have a particular variant of this warrior gene, you are going to be predisposed toward violence. So he believes that serial killers have both a different brain function and a different genetic makeup.

CONAN: Now, it's interesting. In one of the stories you did, you talked with Jim Fallon, and among the things he did, he's using scans called PET scans, which are one kind of brain scan, and, well, among the people he tested was himself.

HAGERTY: Right.

Mr. JIM FALLON: If you look at the PET scan, I look just like one of those killers. I have the pattern, a risky pattern. In a sense, I'm a born killer. It was, frankly, a little disturbing.

You know, you start to look at yourself, and you say: I may be a sociopath. I don't think I am, but this looks exactly like psychopaths, sociopaths, that I've seen before.

CONAN: So he's got the image.

HAGERTY: Yes, you know, I've got to tell you, it's the best part of this story. About four years ago, he was at a barbecue with his mother, who was then 88 years old, and he was telling her about the science he was doing, and she said, well, Jimmy, you know, have you looked at the people in your family, your ancestors on your father's side? They're a bunch of cuckoos there.

CONAN: Of course on his father's side.

HAGERTY: On his father's side. She was, you know, quick to point that out. It turns out that in his ancestry, about eight people have been accused of murder, including Lizzie Borden - you know, Lizzie Borden, right, took an axe...

CONAN: Took an axe, gave her mother 40 whacks.

HAGERTY: Right, exactly. And so what he decided to do with this little, you know, family experiment, he got family members, his brothers, sisters, mother, wife, all his children, to do brain scans. And he also did genotyping on all of them, to see if they had the brains and the genes of a serial killer. It turns out, everyone's normal except for him.

CONAN: And obviously, though, he's not a serial killer - or at least not that we know of.

HAGERTY: Right, right. And that brings us really to the third part or the third thing that you need, he believes, to be a serial killer, and that is you need to have been abused as a child. You need to have experienced violence as a child.

So it's both nature and nurture, and it was interesting because he said this really changed his view of nature and nurture. He used to believe everything was determined by genes and brain function. But now he doesn't believe it. He thinks that, you know, maybe his great childhood was the reason that he's not behind bars right now.

CONAN: So you can have a genetic disposition, but that is not fate.

HAGERTY: That's right, exactly.

CONAN: And so as he's going through this research, well, is it just sociopaths - psychopaths as he calls them - that look this way?

HAGERTY: Well, I think no, there are probably a lot we don't know. We haven't brain-scanned the entire population. But what we believe, what he believes, is that there are a lot of people out there with brains like his, people who have kind of psychopathic or sociopathic tendencies, who are not acting on those tendencies, who are making the right decisions, in other words.

And, you know, maybe we don't know exactly why. It's a very young science, I have to say that. But probably, part of it has to do with upbringing, that that is a brake on that bad behavior.

CONAN: You can be taught how to control these passions.

HAGERTY: That's right.

CONAN: in the meantime, though, even though it's a young science, it's being quick to be picked up by defense attorneys, who say wait a minute, this may help my client, well, maybe not get off from the crime, but, you know, explain why some behavior was more violent.

HAGERTY: Right, that's really one of the surprising things. Something like in something like 1,200 cases, neuroscience evidence has been presented. And if I can, let me just tell you about one of them that I found was so interesting.

There was a case in Tennessee, the case of Bradley Waldroup. And in 2006, Bradley Waldroup got into a fight with his wife and his wife's friend, who was there, ended up killing his wife's friend, a woman, shooting her eight times, going after her with a machete and then going after his own wife with a machete. So it was really, really gruesome - his four kids were watching this all go on.

And the prosecutors - it was pretty, kind of an open-and-shut case. Everyone knew who did this. But the prosecutors asked for the death penalty. But unfortunately for them, the judge let in evidence about Bradley Waldroup's genes, and he let it be put before the jury. Usually, it's only in the mitigation phase, the death penalty phase.

CONAN: The sentencing phase, yeah.

HAGERTY: Right. And so what the defense attorneys did, is they had William Burnette, who is a forensic psychiatrist at Vanderbilt University, not only analyze him but also genotype him to look for guess what? the warrior gene, the MAOA gene.

It turns out that Bradley Waldroup has the high-risk version of the warrior gene. And in court, William Burnette argued that while the gene didn't make him more violent, it increased the chances of him being more violent or snapping.

And here's what happened. I talked to several jurors, and they said, now, look, the genes weren't the only thing that we considered, but it was one factor; and instead of giving him the death penalty, as the prosecutors asked for, they gave him voluntary manslaughter. They agreed that that gene probably made him snap, and therefore, he shouldn't be put to death.

CONAN: And that is where this really gets interesting, because I think a lot of people, and we heard I your pieces, would argue look, a lot of people have problems, depression and all kinds of other problems with their brain. Does this give everybody an excuse?

HAGERTY: Well, I know. That is one of the really troubling things. I mean, Steven Ericson(ph), a forensic psychiatrist and lawyer, talks about this. He says, you know, alcoholics, alcoholism makes your brain different. It gives you kind of brain abnormalities. Does that mean that an alcoholic who kills someone while driving drunk should suddenly be able to argue hey, my brain made me do it, therefore I'm not as culpable.

This really opens a whole can of worms. This my brain made me do it, my genes made do it, is potentially a very well, it's going to really challenge our legal system. Some people believe that it will really cause a revolution in the legal system.

CONAN: Well, before we get there, I mean, brain abnormalities, what's a normal brain? Everybody has brain abnormalities.

HAGERTY: Right, you do, I do, everyone has brain abnormality - because, you know, the normal brain is the average of everyone. And so what are we going to do, slice and dice, everyone gets a brain scan when they are, you know, accused of some crime, and you're able to say, well, because of this abnormality or that one, I should get a lesser sentence - maybe not off the hook, but a lesser sentence.

And I think a lot of people have a lot of trouble with that. The other thing that they worry about is also that this kind of these brain images, if presented to juries, can be very misleading.

You know, someone can look at that and go, oh, look at the pretty blue there, and oh, it's, you know, yellow there, and his brain really is different from a normal brain. And they could say, well, that just means that he can't be he isn't culpable.

CONAN: Well, it seems to me that defense attorneys ought to be careful about what they ask for because this is a two-sided weapon, no?

HAGERTY: You're absolutely right. In fact, in one of the cases I looked at, the public defenders were very upset that FMRI, brain-scan evidence, was used. And the reason they were so upset is people, jurors could just as easily say, you know, that's a brain abnormality. That is not going to change. This guy is a danger to society. We're going to give him the ultimate penalty, whether it's life in prison or the death penalty. So it could really backfire.

CONAN: And could it eventually come up in cases like parole hearings, something like that?

HAGERTY: Absolutely. Absolutely, it could. And they, you know, the kind of downside for people with these abnormalities is - say you're put in civil confinement. You know, after you serve your sentence, you could be put in civil confinement because you're still considered a danger to society.

Well, who decides whether you get out? It's not just that you've served your time. You know, the folks who are making those decisions could say, you know, he still has this brain abnormality, we're not he's not safe. He's not safe to be put out in society.

CONAN: Twelve-hundred criminal cases - it's been introduced thus far. Has it come into civil court?

HAGERTY: Actually, I think the 1,200 includes both criminal and civil, but the large majority, as I understand it, are criminal cases. Now, you might we are beginning, beginning to see some civil cases. You see it in areas like when someone gets in an accident, and they say that they can no longer concentrate, you know, since they've had this car accident.

Well, now brain scans are beginning to be entered to show that, you know, in fact, he does have a brain dysfunction. There is damage here, and he's not faking it.

A much more controversial area that hasn't really come up yet, but people are talking about it, is child custody cases. You know, you could say oh, you know, my ex-husband has the warrior gene; or my ex-husband has this brain dysfunction, and that inclines him towards violence. I don't trust my children around my ex-husband anymore.

So you can see where this is going. It's very controversial.

CONAN: And some child custody cases, sadly, well, nothing is excluded from use by one side or the other.

HAGERTY: That's absolutely right.

CONAN: Barbara Bradley Hagerty, stay with us. When we come back, we're going to be discussing more in detail about the uses of this neurolaw evidence in the courtroom.

So we want to hear from those of you who have come into contact with it as prosecutors, as defense attorneys, as well, if you're an expert who's testified, give us a call, 800-989-8255. Email us, [email protected] Stay with us. I'm Neal Conan. It's the TALK OF THE NATION from NPR News.

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CONAN: This is TALK OF THE NATION. Im Neal Conan in Washington. We're talking with NPR's Barbara Bradley Hagerty about her series of reports on the criminal brain.

Breakthroughs in neurosciences aren't challenging just the way we think about criminals. They're also beginning to change legal prosecutions and defense in court, what's become known as neurolaw.

We want to hear from those of you who have dealt with criminals as lawyers or in law enforcement. Have you come in contact with neurolaw? Does neuroscience have a place in the courtroom? 800-989-8255. Email us, [email protected] You can also join the conversation on our website. Thats at npr.org. Click on TALK OF THE NATION.

Stephen Morse is a professor of psychology and law at the University of Pennsylvania. He joins us from a studio in Philadelphia. Nice to have you with us today.

Professor STEPHEN MORSE (Professor of Psychology and Law in Psychiatry, University of Pennsylvania): Thanks very much for having me.

CONAN: And Joshua Greene is an assistant professor of psychology at Harvard, with us from a studio in Cambridge. Nice of you to be with us.

Professor JOSHUA GREENE (Assistant Professor of Psychology, Harvard University): Hi, thanks.

CONAN: And Stephen Morse, let me begin with you. Neurolaw, how is affecting the legal system?

Prof. MORSE: Well, very little. The number of cases that Barbara Hagerty has referred to I think is overestimated, although it's very hard to get precise statistics about this.

The whole idea of neurolaw is now a sort of on-the-come, what's going to be in the future because there hasn't been much change in actual legal practice yet. Yes, there have been some cases where the evidence has been admitted, but not very many, and in many cases, it's been excluded, and the exclusion has been upheld.

But the real question is: As neuroscience advances, as it surely will, what should the law look like in the future as we learn more and more about the relation between brain and behavior?

CONAN: And Joshua Greene, what do you think? What should the law look like?

Prof. GREENE: Well, I think that the introduction of new neuroscientific data really cuts to the heart of an old philosophical question about why we are punishing in the first place. And one of the reasons, which has been alluded to before, is what you might call the utilitarian reason, which is that we punish people in order to prevent them and to deter others from committing crimes in the future.

And that rationale, I think, stands no matter what. The question is whether or not this other rationale, which is considered very important by some people, other people think it's a big mistake, which is the retributivist justification, that is punishing people simply to give them what they deserve.

And my sense is that what these new data are doing are poking at people's intuitive sense of justice. And because we're of two minds about punishment and of two minds about dessert and free will and responsibility and all of the complicated philosophical things like that that are lurking behind legal decisions, I think that's where this is really that's where this is really forcing us to rethink things.

CONAN: And Stephen Morse, let me get back to you on that. As this new evidence comes into consideration, if you will, precedents are being set all over the place, are they not?

Prof. MORSE: Not yet but conceivably in the future, yes. So Josh really raises a very, very interesting point. One question is what people will come to believe as a result of advances in neuroscience, genetics and the like, and the other is what they should believe, whether or not the advances and the findings really should cause us to rethink our fundamental notions of justice, that people should get what they deserve. We shouldn't punish people unless they deserve it, no more than they deserve.

The question is whether neuroscience will really cause us to rethink that point of view, and nothing in the neuroscience today I think causes us to do that. What will happen in the future as we discover more things about ourselves, especially when we figure out how the mind really is related to the brain, who knows what the world will look like then?

As for now, I think our very wide range of moral concepts we employ, including what Josh calls the utilitarian and the retributive, are likely to remain secure.

CONAN: And I wonder if there was a concept that was raised in Barbara's pieces called one of the scientists suggested we don't execute any more people with low IQs. If there's an equivalent to that of an emotional IQ, where somebody can be demonstrated scientifically to have less capacity to control their emotions than others, could that become one of the factors that you consider in sentencing?

Prof. MORSE: It certainly could become one of the factors, but notice deciding that that is the kind of factor we should consider is a moral judgment, it's not a scientific judgment.

Once we decide that we want to consider let me speak more generally now the capacity for self-control as a criterion of responsibility such that if it is sufficiently diminished, we would not want to give people the maximum penalties. Once we've decided that, then science may be able to help us discover which people have diminished capacity in that respect. But deciding whether that should be a criterion is not a scientific question to begin with.

CONAN: Joshua Greene, a scientific question or a moral question?

Prof. GREENE: Well, I agree with Professor Morse that it is indeed a moral question, but I think it's a moral question that we have deep intuitions about. And I think the core of the intuition goes something like this: We don't want to punish people for things that are beyond their control. No one chooses their genes. No one chooses the circumstances of their early childhood. And more generally, if you think of someone's behavior as ultimately a product of their genetic inheritance and the circumstances in which they find themselves, then unless you believe that there's some extra-special you that's above and beyond your physical self, then in a sense, everything is ultimately beyond your control.

Now, that's not to say that things aren't in a sense within your control. We have beliefs, and we have desires, and we have intentions and values, and we act on those things. But the thought is that if you chase those things far back enough, you're going to find things that are beyond your control.

And so I think a lot of people have the reaction, well, if this gene was a critical factor, or if this brain tumor was a critical factor, then I don't want to hold that person fully responsible.

Now, one way to go is to develop a consistent philosophy that says look, we may have these intuitions, but it just doesn't matter, and then specify what exactly it is that matters.

Another and this again a moral judgment another thing you can do is look at that and say okay, we think that intuition is right. But if it's right, then how does the law need to change to accommodate that.

HAGERTY: You know, if I can jump in here, I have a couple of questions, and one is the MacArthur Foundation is just an observation the MacArthur Foundation is really, really looking at this. They've thrown $10 million at the issue of neurolaw, and it's actually researchers from working with a...

Prof. MORSE: Barbara, let me interrupt you for just one second. Joshua and I are both members of the project.

CONAN: Okay.

HAGERTY: Right, right, and some of the researchers I knew that and some of the researchers there were the ones actually that unearthed this notion of 1,200 cases. They went through, like, in the state of California looking at one after another. It was very tedious work.

But a lot of people do think that neural science is like DNA. Just as DNA, people looked at it a little warily at the beginning, now it is standard operating procedure in the courtroom. And a lot of people believe that neuroscience will be, as well.

And I guess one thing I would wonder is what we're arguing here on this what we're arguing here, it's not that some of these people don't know the difference between right and wrong. We're not arguing, say, that a psychopath doesn't is hearing voices and thinking that God told him to kill that little girl. We know that these people know the difference between right and wrong. Doesn't the law care about whether you knew the difference between right and wrong at the time of the crime? Isn't that an important distinction? Or is that distinction just going to go away?

CONAN: Stephen Morse, you want to try first?

Prof. MORSE: Sure. Yes, we now consider the ability to know right from wrong to be an important criterion for criminal responsibility. Why? When we're thinking about human beings guiding their own behavior, one of the things we're most guided by is our moral compass, our set of knowledge of right and wrong. If you don't have that knowledge, then it's going to be very hard for you to behave well.

Now, the interesting thing about the psychopath is they can tell you true-false right or wrong, but the question is whether they really understand what it means, right versus wrong, whether it's just a true-false test or whether it's something that they've assimilated that they can actually use in their reasoning. And that is a matter of major dispute. The law now does not excuse psychopaths, but there are many people who think it should, even though it would then produce a very grave practical problem.

But notice what your question implies. It implies that you've got an acting human being. You don't just have a mass of neurons. And as long as we have acting human beings, to whom the law is addressed, then I think much of our fundamental ideas of justice, dessert and consequential concerns of the sort Joshua Greene raised will remain intact.

CONAN: Let's get a caller in on the conversation, 800-989-8255. Email us, [email protected] Colin(ph) is with us from Cookeville in Tennessee.

COLIN (Caller): Hi, well, I'm going to (technical difficulties) from a slightly different angle. I'm not law enforcement, but I was convicted of armed bank robbery, and I got six months in a halfway house and six months of house arrest due to a diagnosis of dysthymia, a chronic depression.

CONAN: Chronic depression. So obviously, six months for armed robbery is very light time.

COLIN: Yeah, and it was in a halfway house, too, so they didn't even sentence me to prison time. They called it a downward departure due to aberrant behavior, I just snapped.

CONAN: And do you agree with the diagnosis, or are you sitting there saying ha-ha?

COLIN: Well, you know, it's hard to say. On one hand, I look today, and I say, well, (technical difficulties) know what people should get away with. But on the other hand, I see that people do get pushed to their limits. They do snap. And, you know, I'd never been in trouble before and since - I haven't been in trouble since.

And I've used my freedom to be a better father, a better person in the community. I'm involved with Dismas House. I've volunteered for five years. I went in every week to the public jail and brought in a 12 step program. And I've just - to be a better person. I stayed in the community, too. My now ex-wife wanted me to moved and never speak of this again, but I stayed and faced the ridicule and the derision and have tried to redeem myself to this community.

CONAN: Joshua Greene, Collin raises a number of issues. But among them, the thin end of the wedge issue. If you're going to get less culpability for emotional distress of one type or another. Where does that end?

Prof. GREENE: Right. So I think that one place where it certainly needs to end is the recognition that there is the other set of criteria for when it makes sense to punish someone or not. So independent of what we think about justice and desert in some grand metaphysical sense, there's certainly the challenge, the problem of preventing future crime. And even if you think that someone doesn't, deep down in their soul, deserve to be punished, if you think that punishing them is going to prevent them or prevent other people from committing crimes, then that's, I think - I think most people agree - a valid reason for punishing somebody.

Now, not everybody takes this view. For example, you had Kent Kiehl on earlier. And if I read him correctly, what he's saying is that the only thing I really care about is justice in the abstract sense, and I think it's unjust to punish somebody if they have some kind of disability such as being a psychopath or something a bit more mild, as what was described here. So I think that...

CONAN: Yeah. We're actually going to be talking with him in a bit. But, yeah, go ahead.

Prof. GREENE: Okay. So I think that that's one place where, so to speak, it does end. This worry that, well, everything has its brain problems that go along with it, does everybody get off the hook? And I think the answer may be, in an ultimate metaphysical sense, perhaps everybody should be off the hook. But in a practical sense, there are going to be some people who need to be on the hook and some people who don't, depending on what we expect the effects of our social sanctioning to be.

CONAN: Collin, thanks very much for the phone call. We appreciate it.

COLLIN: Thanks for having me on.

CONAN: All right. Bye-bye. We're talking about neurolaw with NPR's Barbara Bradley Hagerty. Also with us, Stephen Morse, a professor of psychology and law in psychiatry at the University of Pennsylvania, and Joshua Greene, an assistant professor of psychology at Harvard University. And you're listening TALK OF THE NATION coming to you from NPR News.

And let's get Mike(ph) on the line. Mike with us from St. Paul.

MIKE (Caller): Yes. Hi, Neal. Good to be on. I was a major in philosophy and psychology and I'm definitely no legal expert. But - and a lot of my questions have kind of been addressed already. But I guess what the real question for me, is how do we have a legal system that does not incorporate metaphysical or religious belief, you know, just kind of as a given because...

CONAN: Well, though we have a legal system that does incorporate them, it just depends which ones, doesn't it?

MIKE: Well, yes, yes. And I think that, you know, from everything that I've learned, the whole idea of kind of the ghost in the machine and freewill and these kinds of things, there are so many problems with them. And, you know, it's the idea that my brain made me do it is - you know, our brains make us do everything. There is nothing else to make us do what we do.

CONAN: Right.

MIKE: So...

CONAN: Well, Stephen Morse, let me turn to you on this. You've described this in other circumstances as a neuro arrogance.

Prof. MORSE: Well, there are two questions, one is claiming we know more about the relation between the brain and behavior than we actually do. But the other is the conceptual question that the caller raises, which is whether the law has certain kinds of commitments about the nature of a human being and the nature of society and the like, which the caller referred to as metaphysical. And I think the answer is, yes, the law does have a concept of the person. And that's a creature who can be guided by reason, who - for whom you can give reasons and to whom reasons appeal.

And, yes, it's true that if you're brain is dead, you have no reasons. But that doesn't mean we have - don't have reasons, we do, and they can be appealed, too. And that's the kind of creature the law presupposes. And as long as the law presupposes that kind of creature, then many of our most important concepts will continue intact.

Now, we all want the criminal justice system to make us safer. We want it to deter crime. We want to keep dangerous people off the street. But if all you're concerned with is the sort of social safety issues, then whether if someone is responsible or not in some important way, whether or not someone deserves to be locked up, drops out. And that leads to a real, in my view, social dystopia that we don't want to approach. And I don't think there's anything in neuroscience, yet, that says we have to.

CONAN: Mike, thanks very much for the call.

MIKE: Thank you, Neal.

CONAN: And let's see if we can get one more caller in. This is Bill(ph), Bill with us from Boston.

BILL (Caller): Yes. I just have a very - what I think is a simple question. I haven't looked at the research to see if, in fact, the study has been done. I'm a licensed PhD psychologist working in the statistics field. I'm wondering, has anyone simply looked at a random sample of people, looking at their criminal record, and looking, maybe, at their fMRI profile to see if there is, in fact, any correlation?

CONAN: Barbara Bradley Hagerty, I don't think...

HAGERTY: I don't think...

CONAN: ...all that many of us have that...

HAGERTY: Right. I don't...

CONAN: ...fMRI file.

HAGERTY: Right. No, I don't think so. I'd be interested in knowing if our guests have any idea about that because I haven't heard of that.

CONAN: Any - either one of you, Stephen Morse or Joshua Greene?

Prof. MORSE: I haven't.

Prof. GREENE: As far as - I mean, there has been no...

Prof. MORSE: I mean, there haven't...

Prof. GREENE: ...sorry - there's been no mass effort to do a wide screening of a large portion of the population. Earlier, we mentioned Kent Kiehl who has scanned the brains of many inmates and also many normal individuals. So, you know, he has done as much as anyone to sort of put his finger on what is the difference between typical people in the normal population, people who are in prison, and people who are in prison and who are psychopaths. But we certainly don't have anything like the neuro equivalent of a big fingerprint or DNA database.

CONAN: Okay. Bill, thanks very much. It's a provocative question, maybe more relevant in years to come.

BILL: Okay.

CONAN: Appreciate the call. And, gentlemen, thank you so much for your time today.

Dr. GREENE: Thank you.

CONAN: Stephen Morse...

Dr. MORSE: Thank you very much.

CONAN: ...is a professor of psychology and law in psychiatry at the University of Pennsylvania; and Joshua Greene, assistant professor of psychology at Harvard. They mentioned Kent Kiehl. He's studied the brains of murderers and other criminals, including Brian Dugan, a man serving two life sentences for the rape and murder of a 10-year-old girl.

Professor KENT A. KIEHL (University of New Mexico): Cognitively, he appreciated that he was committing a crime and that he was doing a bad thing and that, you know, he's likely to spend the rest of his life in prison or on death row if he did this. But the emotion and the affect and whatever typically causes the rest of us to really never even contemplate something like that, didn't come to pass.

CONAN: We'll talk about what happens inside a psychopath's brain. Barbara Bradley Hagerty will stay with us. We hope you do, too. I'm Neal Conan. It's the TALK OF THE NATION from NPR News.

CONAN: Right now, we're talking with NPR correspondent Barbara Bradley Hagerty. Her series on the criminal mind, the brain and DNA traits shared by some violent criminals ran last week on MORNING EDITION. If you missed any of it, you could listen online. Go to npr.org for that.

Psychopath is one of those terms of art that many of us probably use too freely. In fact, the definition is quite specific and technology can now provide new insights.

Kent Kiehl studies the brains of psychopaths. He's the director of Mobile Imaging Core and Clinical Cognitive Neuroscience at the University of New Mexico and joins us now from his office. Nice to have you with us today.

Prof. KIEHL: Thank you for having me.

CONAN: And that definition, what is a psychopath?

Prof. KIEHL: The classic definition is someone who has real profound difficulties understanding empathy, guilt and remorse. They're pretty glib and superficial, somewhat charming. They tend to get themselves in all sorts of trouble, from - starting from a very early age. They're impulsive, they're nomadic, they jump in and out of relationships very quickly. And sometimes they do, you know, extremely bad things that tend to come to the attention of the criminal justice system.

CONAN: And is there a meaningful distinction between a psychopath and a sociopath?

Prof. KIEHL: That's really an evolution in terminology. The term sociopath was really meant to convey social forces have molded this individual to be this way. That was a behaviorist era term in the '70s. And psychopathy, or psychopathic personality, is a term that has kind of predated that and is now more the in-vogue or the, kind of, current, kind of, nomenclature we use now.

CONAN: And what are the things that you've been able to do with new technology, is literally look inside the brain?

Prof. KIEHL: Yes. We've been using a mobile MRI system and deploying that to regional facilities around the country, to work with individuals who are incarcerated who have psychopathy, to try to understand them in bigger numbers than we've been able to do by working with them just in the community.

CONAN: And bigger numbers - how many have you looked at?

Prof. KIEHL: In the past two years, a little over 1,100 inmates have volunteered for research, so it's quite a large database.

CONAN: And what brain patterns do they share in common?

Prof. KIEHL: The individuals who score really high in psychopathy, we're tending to find that older emotional areas of the brain, the regions that we refer to as limbic or even paralimbic regions, tend not to be engaged in the same way when they're processing different moral stimuli, for example, or when they're processing emotional stimuli, compared to individuals who are incarcerated but don't have psychopathy.

HAGERTY: Kent, can you just explain - you know, you've done an experiment where you show various pictures? It helped me understand it. Can you just explain what you did with that?

Prof. KIEHL: Sure. So in one of our studies, which is just now in press, we used three different types of pictures. One type of picture might depict kids who are looking over a Bunsen burner. That would be a neutral picture. People would rate that as not having a significant moral violation or moral content. And that will be contrasted to other pictures that might display like, you know, individuals around a burning cross, like a Ku Klux Klan picture. And most individuals rate that as having high moral contents or representing a moral violation. And then we would also contrast that to other emotional pictures that dont have moral content. So, for example, like a car that's burning. And so, we're interested in understanding the emotional responses in the brain when people are trying to make those judgments.

CONAN: And you show them those pictures while they're in the fMRI?

Prof. KIEHL: Yes. While they're in the MRI scanner, they're making decisions and they're viewing those pictures. And then we're studying how their brain responds while they're doing those - that task.

CONAN: And when you talk about the limbic system, that's the amygdala that we were talking about earlier?

Prof. KIEHL: Yes. That's a favorite for most people. The amygdala, the orbitofrontal cortex, the anterior cingulate cortex, those are kind of the centerpieces of the limbic system.

HAGERTY: And they don't light up in the same way that a normal person's brain -limbic system - would light up. Is that right?

Prof. KIEHL: Yeah. Well, in particular, we find that that orbitofrontal cortex doesn't appear to be engaged when they're seeing any affective pictures. And so this suggests that when they're viewing those pictures for the first time, those emotional pictures, they're not able to tap into it or we're not getting the same kind of response in them as we do in individuals who don't have these characteristics.

CONAN: And when you said earlier that somebody who scores high on psychopathy -explain what you mean by scoring high.

Prof. KIEHL: So there are officially about 20 characteristics. Then each of the characteristics of psychopathy are scored on a two-point scale, in the forensic way we assess the condition. And so if you score high on almost all of those items, you need to score almost 30 out of 40, or 30 out of 40 in order to kind of officially meet the criterion for what we're studying.

CONAN: And so, somebody who scores 30 out of 40. And I wonder, have you looked - done one of these fMRI examinations on anybody who scored very high and found that they did not - their brain did not look like that?

Prof. KIEHL: That's a great question. We actually haven't. We're kind of typically now looking at groups, you know, large numbers of groups to try to say with some specificity that a certain person that looks, you know, like, has all the criterion for psychopathy and doesn't engage the system. I don't think the science is quite there yet.

CONAN: And I wonder, obviously, you're still in early phases - 1,100 may sound like a lot, but I'm sure you want a lot more data before you come to conclusions. But the implications of this are fascinating.

Prof. KIEHL: Yeah. I mean, I agree with you and I hope that - you know, our goal by studying these large numbers is to try to really understand all of the different influences and (unintelligible) and issues that might lead someone to come on this path or to have this condition.

And the ideal is to be able to start intervening as early as possible, to try to treat, to try to get them back on the right track. Because all of the guys that we work with who were, you know, in prison for five or 10 years, they've all typically had a long history of getting in trouble. And if we could have identified them early and then steered them off this trajectory, it would have been the best thing for them as well as for society.

HAGERTY: You know, one of the things, Kent, that I heard about a lot was that people feel that psychopath's brains don't change over time. In fact, something that you said to me was very interesting. You said you've looked at the brains of psychopaths who are 50 and those who are 25, and they looked very much the same, that a psychopath's brain basically looks the same. Why then do you think that a psychopath can be rehabilitated? Why do you think that their brains can change?

Prof. KIEHL: Well, I think we have good evidence from - when they're youth. There's a treatment program in Wisconsin run by a guy named Michael Caldwell. And hes actually been able to show that in these highest risk kids, these kids that score very high on the youth version of the psychopathy checklist, he can take those kids and put them in very intensive treatment.

So, this isn't, you know, three days and you're out. This is like nine months to a year of intensive cognitive behavioral therapy. And that is then followed by those kids in his group showing a reduced recidivism rate of over 50 percent for violent recidivism. So that would suggest that there has been some change in their brain over time while they're doing this treatment program.

And so if we could study those kids and find out how they change exactly, that would be ideal. But I think that most of us, scientists would agree that the brain continually changes throughout your life, and even an individual's psychopathy are capable of change. It's just going to take a lot of effort and it's going to take potentially long term, you know, implementations of treatment in order to try to see that change come through.

CONAN: Earlier, we heard a story about Jim Fallon(ph), the scientist who did his own PET scan and found that he looked like a natural-born killer. And what he said was, you know, there have to be three things: yes, there's the brain pattern; yes, there's the gene; but there's also abuse when you're growing up. And he attributed the fact that he is not a natural-born killer to the fact that he had a great childhood.

Prof. KIEHL: I don't know that I can necessarily agree with him, but I think that we find - in psychopathy, in particular, we find that they come actually from kind of all walks of life. So, some actually come from good backgrounds, some come from not-so-good backgrounds, and some come from really bad backgrounds. And, you know, we're trying to understand how those different forces interact, you know, from the environment, the genetics and the biology, in order to lead someone to be like that.

CONAN: Here's an email from Dolly(ph) in Williamsburg, Virginia. Id like to know the sense in which your guest is using the term psychopath. I work in forensic psychology, treating NGRIs, and I find that those with axis one disorders like schizophrenia or bipolar disorder tend to respond to treatment and get out of the hospital with good prognosis. Those with an antisocial or other personality disorder often can't deal with the intensity and structure required.

When a person has not - has been adjudicated NGRI, they rail against the restrictions, try to gain the system. They do better in jail and often get out sooner than they would've gotten out of the hospital. They seem to respond better to this reward/punishment paradigm. Having a low level of moral development, would the neurologically predisposed patient be more treatable as opposed to needing to remain hospitalized or incarcerated? And while you're answering, you might tell us what NGRI is.

Prof. KIEHL: So NGRI stands for not guilty by reason of mental disease or insanity. And typically people who have committed a crime in the context of being psychotic like schizophrenia or a bipolar illness, and then when you treat the illness there, the underlying cause, that tends to have them get back and be very manageable and get released back into the society. So - and that's great if you can actually implement that kind of a treatment.

And what she's saying is the classic kind of antisocial personality or having psychopathy, that they're very resistant to standard forms of treatment. And so you might actually be surprised that there aren't - isn't even a single randomized placebo control study of treating psychopathy that's ever been published.

And so a lot of people don't spend a lot of effort to try to develop treatment programs that work with this population because, you know, when you treat somebody who has depression, for example, and they get up out of bed, you know, and go back to work, that's a great thing. And if they get depressed again, they go back to getting - going to bed and don't want to go to work. And that's easy for a clinician to deal with.

But when you work with individuals with psychopathy, you know, the outcome measure that they might have killed somebody or they might have robbed another bank or done something really bad, and that can be harder to deal with. So there's not a lot of clinicians that really want to work with remediating this condition. Like I'm...

CONAN: I want to get, quickly - one caller has got a question. I want to get to it quickly - we just have a little time left. Paul(ph) is with us from Grand Rapids.

PAUL (Caller): Hi, I'm a corrections officer and I work in one of my states prison. And one of the things that I see on a pretty regular basis is prisoners who abuse the mental health system by manipulating it, manipulating diagnosis and stuff like that.

And so the question I have is a practical one, and I understand it may be difficult to answer. Once we've identified these individuals, what are we actually going to do to help them? I just heard the speaker talk about how it's hard to find psychologists. And that's actually a difficulty that we have is once they get inside the prison, they're faced with a pretty overwhelming environment that's pretty violent and pretty negative at any given moment.

CONAN: Mm-hmm.

PAUL: What are we actually going to do once we identify these kids? Are we going to make better schools, betters psyches? What are we going to do to help?

CONAN: And Kent Kiehl, we'll give you a whole minute to answer that.

Prof. KIEHL: Sure. Well, like I said, I think that the state of Wisconsin has got that correct in the sense that if someone came to them with that exact same problem and said, well, what can we do to remediate these highest risk kids, these kids that have a 90 percent chance that when they're released from juvenile custody they're going to end up in prison as an adult? And again, he's one of my heroes, and again his name is Michael Caldwell. And what he designed was a very intensive treatment program, and he convinced the state to then fund it.

And they went and they treated several hundred kids who were in the highest risk group in the entire state. And then they followed those kids up, and they compared them to other kids that are treated in the facilities just as normal, so the average kind of kid, and who was incarcerated, mind you. And what they found was that this intensive treatment program that he design actually shows a huge reduction of violent recidivism, 50 percent.

CONAN: But, very quickly, would that same kind of treatment help somebody 35, 50 years old?

Prof. KIEHL: That's a great question. I would like to start with young offenders and then move to adolescent or - I mean, then move to first-time offenders and then move to then yet adult offenders. Maybe it just takes three or four times longer to change those attitudes and behaviors in the older offenders than it does in the younger offenders.

CONAN: Paul, thanks very much for the call. We appreciate it. And Kent Kiehl, thank you so much for your time today. We appreciate that.

Prof. KIEHL: Well, thank you very much for having me.

CONAN: Kent Kiehl studies the brains of psychopaths. He's a professor at the University of New Mexico and joined us today from his office. Our thanks as well to NPR's Barbara Bradley Hagerty. Again, go to npr.org, click on TALK OF THE NATION. There's a link to her series that was broadcast last week on MORNING EDITION. This is TALK OF THE NATION from NPR News.

NPR transcripts are created on a rush deadline by an NPR contractor. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.

Scans of a normal brain, left, beside that of murderer Antonio Bustamante

How to spot a murderer's brain

I n 1987, Adrian Raine, who describes himself as a neurocriminologist, moved from Britain to the US. His emigration was prompted by two things. The first was a sense of banging his head against a wall. Raine, who grew up in Darlington and is now a professor at the University of Pennsylvania, was a researcher of the biological basis for criminal behaviour, which, with its echoes of Nazi eugenics, was perhaps the most taboo of all academic disciplines.

In Britain, the causes of crime were allowed to be exclusively social and environmental, the result of disturbed or impoverished nurture, rather than fated and genetic nature. To suggest otherwise, as Raine felt compelled to, having studied under Richard Dawkins and been persuaded of the "all-embracing influence of evolution on behaviour", was to doom yourself to an absence of funding. In America, there seemed more open-mindedness on the question and, as a result, more money to explore it. There was also another good reason why Raine headed initially to California: there were more murderers to study than there were at home.

When Raine started doing brain scans of murderers in American prisons, he was among the first researchers to apply the evolving science of brain imaging to violent criminality. His most comprehensive study, in 1994, was still, necessarily, a small sample. He conducted PET [positron emission tomography] scans of 41 convicted killers and paired them with a "normal" control group of 41 people of similar age and profile. However limited the control, the colour images, which showed metabolic activity in different parts of the brain, appeared striking in comparison. In particular, the murderers' brains showed what appeared to be a significant reduction in the development of the prefrontal cortex, "the executive function" of the brain, compared with the control group.

The advancing understanding of neuroscience suggested that such a deficiency would result in an increased likelihood of a number of behaviours: less control over the limbic system that generates primal emotions such as anger and rage; a greater addiction to risk; a reduction in self-control; and poor problem-solving skills, all traits that might predispose a person to violence.

Even two decades ago, these were difficult findings to publish, however. When Raine presented a far less controversial paper in 1994 to a peer group, one that showed a combination of birth complications and early maternal rejection in babies had significant correlation with individuals becoming violent offenders 18 years later, it was denounced as "racist and ideologically motivated" and, according to Nature magazine, was simply further strong evidence that "the uproar surrounding attempts to find biological causes for social problems will continue". Similarly, when, 15 years ago, at the urging of his friend Jonathan Kellerman, the child psychologist and crime writer, Raine put together a proposal for a book on some of his scientific findings, no publisher would touch it. That book, The Anatomy of Violence , a clear-headed, evidence-based and carefully provocative account of Raine's 35 years of study, has only now appeared.

The reason for this delay seems mired in ideological enmities. For all Raine's rigour, his discipline of "neurocriminology" still remains tarnished, for some, by association with 19th-century phrenology, the belief that criminal behaviour stemmed from defective brain organisation as evidenced in the shape of the skull. The idea was first proposed by the infamous Franz Joseph Gall, who claimed to have identified over- or underdeveloped brain "organs" that gave rise to specific character: the organ of destructiveness, of covetousness and so on, which were recognisable to the phrenologist by bumps on the head. Phrenology was widely influential in criminal law in both the United States and Europe in the middle of the 1800s, and often used to support crude racial and class-based stereotypes of criminal behaviour.

The divisive thinking was developed further in 1876 by Cesare Lombroso, an Italian surgeon, after he conducted a postmortem on a serial murderer and rapist. Lombroso discovered a hollow part of the killer's brain, where the cerebellum would be, from which he proposed that violent criminals were throwbacks to less evolved human types, again identifiable by ape-like physical characteristics. The political manipulation of such hypotheses in the eugenics movement eventually saw them wholly outlawed and discredited.

As one result, after the second world war, crime became attributable to economic and political factors, or psychological disturbances, but not to biology. Prompted by advances in genetics and neuroscience, however, that consensus is increasingly fragile, and the implications of those scientific advances for law – and for concepts such as culpability and responsibility – are only now being tested. He draws on a number of studies that show the links between brain development, in particular – and brain injury and impairment by extension – and criminal violence. Already legal defence teams, particularly in the US, are using brain scans and neuroscience as mitigating evidence in the trials of violent criminals and sex offenders. In this sense, Raine believes a proper public debate on the implications of his science is long overdue.

Raine was in part drawn to his discipline by his own background. In the course of scanning his murderers, Raine also examined his own PET profile and found, somewhat to his alarm, that the structure of his brain seemed to share more characteristics with the psychopathic murderers than with the control group.

He laughs quickly when I ask how that discovery felt. "When you have a brain scan that looks like a serial killer's it does give you pause," he says. And there were other factors: he has always had a markedly low heart rate (which his research has shown to be a truer indicator of a capacity for violence than, say, smoking is as a cause of lung cancer). He was plagued by cracked lips as a child, evidence of riboflavin deficiency (another marker); he was born at home; he was a blue baby, all factors in the kind of developmental difficulties that might set his own researcher's alarm bells ringing.

"So," he says, "I was on the spectrum. And in fact I did have some issues. I was taken to hospital aged five to have my stomach pumped because I had drunk a lot of alcohol. From age nine to 11 I was pretty antisocial, in a gang, smoking, letting car tyres down, setting fire to mailboxes, and fighting a lot, even though I was quite small. But at that age I burnt out of that somehow. At 11, I changed schools, got more interested in studying and really became a different sort of kid. Still, when I was graduating and thinking 'what shall I research?', I looked back on the essays I'd written and one of the best was on the biology of psychopaths; I was fascinated by that, partly, I think, because I had always wondered about that early behaviour in myself."

As Raine began to explore the subject more, he began to look at the reasons he became a researcher of violent criminality, rather than a violent criminal. (Recent studies suggest his biology might equally have propelled him towards other careers – bomb disposal expert, corporate executive or journalist – that tend to attract individuals with those "psychopathic" traits.) Despite his unusual brain structure, he didn't have the low IQ that is often apparent in killers, or any cognitive dysfunction. Still, as he worked for four years interviewing people in prison, a lot of the time he was thinking: what stopped me being on their side of the bars?

Raine's biography, then, was a good corrective to the seductive idea that our biology is our fate and that a brain scan can tell us who we are. Even as he piles up evidence to show that people are not the free-thinking, rational agents they like to imagine themselves to be – entirely liberated from the limitations set by our inherited genes and our particular neuroanatomy – he never forgets that lesson. The question remains, however, that if these "biomarkers" do exist and exert an influence – and you begin to see the evidence as incontrovertible – then what should we do about them?

Perhaps we should do nothing, simply ignore them, assume, when it comes to crime, that every individual has much the same brain, the same capacity to make moral choices, as we tend to do now. As Raine suggests: "The sociologist would say if we concentrate on these biological things, or even acknowledge them, we are immediately taking our eyes off other causes of criminal behaviour – poverty, bad neighbourhoods, poor nutrition, lack of education and so on. All things that need to change. And that concern is correct. It is why social scientists have fought this science for so long."

The implication of neurocriminology, though – where it differs from the crude labelling of phrenology, say – is that the choice it presents is not an either/or between nurture and nature, but a more complex understanding of how our biology reacts with its environment. Reading Raine's account of the most recent research into these reactions, it still seems to me quite new and surprising that environmental factors change the physical structure of the brain. We tend to talk about a child's development in terms of more esoteric ideas of mind rather than material brain structures, but the more you look at the data the clearer the evidence that abuse or neglect or poor nutrition or prenatal smoking and drinking have a real effect on whether or not those healthy neural connections – which lead to behaviour associated with maturity, self-control and empathy – are made. The science of this is called epigenetics, the way our environment regulates the expression of our innate genetic code.

One result of epigenetics might be, Raine suggests, that "social scientists can actually win from this. I mean, if a child experiences a murder in his or her neighbourhood, we have found that their test scores on a range of measures go down. There is something happening in the brain as a result of that experience of violence to affect cognition. So social scientists can have their cake and eat it. They can say look, we can prove that these environmental social factors are causing brain impairment, which leads to some real, measurable problems."

One difficulty of embracing this "epigenetical" idea of crime is the degree to which such factors should be taken into account in courts of law. There have been several landmark cases in recent years in which particular neurological disorders caused by blows to the skull or undetected tumours have resulted in arguable changes in character and behaviour – and the violent or sexual crime is blamed on the disorder, not the individual. In most of these cases, it has been argued by the prosecution that brain imaging is prejudicial, that the brightly coloured pictures are too compelling to a jury and more emotional than scientific. But if neural scanning becomes more routine, and neuroscience more precise, will there not come a point where most violent behaviour – that of the Boston bombers, say, or the Newtown killer – is argued away in court as an illness, rather than a crime?

Raine believes that there might well be. He even likens such a shift to our change in perception of cancer, until fairly recently often deemed the "fault" of the sufferer because of some repressive character trait. "If we buy into the argument that for some people factors beyond their control, factors in their biology, greatly raise the risk of them becoming offenders, can we justly turn a blind eye to that?" Raine asks. "Is it really the fault of the innocent baby whose mother smoked heavily in pregnancy that he went on to commit crimes? Or if he was battered from pillar to post, or even if he was born with a, abnormally low resting heart rate, how harshly should we punish him? How much should we say he is responsible? There is, and increasingly will be, an argument that he is not fully responsible and therefore, when we come to think of punishment, should we be thinking of more benign institutions than prison?"

But then there is a further thought, that if you start to see criminality as a biological illness, where does a sense of retributive justice stand?

Raine himself was forced to face this dilemma when he became a victim of violent crime. As he recounts in his book, while on holiday in Turkey several years ago, a burglar entered his bedroom and in the struggle that followed tried to cut Raine's throat with a knife. He fought the attacker off, but when the following morning he was presented with two possible suspects by police, he admits to not only choosing the one who looked most like a thug [the man later admitted the crime, under duress], but also to wanting to visit on him the terror he had felt himself.

"I wasn't proud to discover I was a bit Jekyll and Hyde – perhaps we all are in that situation," Raine says when I ask him about his response. "The rational Dr Jekyll knew that if I took this man's brain scan and found he had prefrontal dysfunction, low resting heart rate, a background of neglect, then of course I should cut him some slack. With understanding comes mercy. But the Mr Hyde, the emotional voice in my head, was saying nothing of the sort: he was saying, he cut my throat, I want to cut his. That event changed me from someone dead set against the death penalty to someone who wouldn't be ruled out of a jury on a capital case in America. I think now my mind will always go backwards and forwards on this, the scientific understanding of the causes of crime versus being a human in society with all these gut reactions to people who commit awful crimes."

If the neuroscience raises as many questions as it answers about culpability after a crime has been committed, what about its role in crime prevention? Here, the questions seem no less fraught.

One of them was posed a couple of years ago by the arch-inquisitor Jeremy Paxman of Shami Chakrabarti , director of Liberty, on Newsnight . "If science could predict with 100% certainty who was going to commit a violent crime, would it be legitimate to act before they commit that crime?"

Chakrabarti was in no doubt: "I would have to say that in a liberal society of human beings, and not animals, my answer to your question would be 'no'."

But if such intervention could prevent Newtown, you wonder, or Dunblane, would any of us be quite so certain? The fact is that the reality will always be a much greyer area because even the most nuanced neuroscience will never produce a perfect prediction of human behaviour. But is there a point at which the science – in identifying the possibility of repeat offending, for example – will be accurate enough to warrant routine scanning of those on the sexual offenders' register?

"The fact is," Raine says, "parole boards are making exactly these kind of predictive decisions every day about which prisoner or young offender we are going to release early, often with crummy evidence. At the moment, the predictors are social and behavioural factors, marital status, your past record. What is not used are biological measures. But I believe that if we added those things even now into the equation, we could only improve the prediction."

Raine cites two very recent brain-imaging studies to back this up. One is a study in New Mexico in which prisoners are scanned on release. "What they are discovering is that if the functioning of the anterior cingulate, part of the limbic system, is lower than normal before release, they are twice as likely to be reconvicted in the next three years. And that marker is more accurate a guide than all other social factors," Raine says. A second study apparently shows if a released prisoner has a significantly smaller volume in the amygdala, the almond-shaped part of the brain crucial for processing memory and emotion, he or she is three times more likely to reoffend. "Now, this is only two studies, but what they are beginning to show is proof of concept, that if we added neurological factors into the equation we could do a better job at predicting future behaviour."

At the end of his book, Raine suggests various possible Orwellian futures of such science, an ethical "slippery slope" of interventions that ultimately imagines a society that assesses the biological risk of all individuals – a wide-scale version of We Need to Talk About Kevin – and pre-emptively locks up those at the extreme end of the curve (a sort of evidence-based Guantánamo). He by no means advocates any of it, though when I ask if he would have his own children, two boys of 11, scanned, he suggests he probably would.

"If there was the opportunity for screening at school or through a GP programme, would I do it? Well, if my kids had problems, as a parent I would want to know about them and I would want to know how I might deal with them. If you brought in such things as emotion regulation and impulse control, which we know are risk factors for behaviour, then to me, as a parent, I would sort of want to know what could be done to help with those."

It is perhaps not too wildly far-fetched to imagine that such scans will one day be as routine as immunisation programmes; the bigger question then will be how we begin to react to the results. Raine rather likes the idea of public health programmes as crime prevention: "The teenage brain is still very malleable. There is good evidence from randomised control testing that omega-3 [fish oil] has a positive effect on young offenders, and even mindfulness seems to improve behaviour and brain structures."

You can't help thinking: if only it were as simple as that.

This article was amended on Sunday 12 May 2013. Adrian Raine is a professor at the University of Pennsylvania, not Philadelphia as we mistakenly said in the original article. This has been corrected.

Inside the head of a killer: Imaging study uncovers unique brain abnormalities in murderers

For decades scientists have been exploring the minds of criminals, trying to understand what makes a person commit a violent, heinous act. The advent of modern brain imaging techniques in the late 20th century proved a boon to the burgeoning field of neurocriminology. Examining the brains of murderers, psychopaths and other violent offenders has unsurprisingly proved to be a controversial scientific pursuit. To some, modern attempts to associate criminal behavior with objective brain imaging skirts discomfortingly close to the controversial 19th century pseudoscience of phrenology.

Phrenology asserted that the shape and contours of a person's skull could be directly associated with a variety of personality traits, from one's intelligence to their propensity for criminal activities. Although the "science" of phrenology was pretty widely discredited by the mid-1800s, its central notion has lingered as a supposed scientific basis for many racist ideas into the 20th century.

Most modern neuroscience looking to find structural or biological signs of criminal and antisocial behaviors in brain imaging data concentrates on more general traits such as aggression or lack of empathy. The neurology of psychopathy is a rich field of neuroscience, with many researchers uncovering fascinating insights into potential brain structures that could underlie certain violent antisocial behaviors.

A new study, published in the journal Brain Imaging and Behavior , is taking this idea of neuroimaging criminal behavior one step further than any prior research. This new research, based on brain imaging data from 808 incarcerated male adults, suggests the brains of individuals that have committed murder are notably different from other criminals, both violent and non-violent.

Specifically imaging the brains of homicide offenders in not especially novel. Pioneering neurocriminologist Adrian Raine conducted some of the earliest neuroimaging studies on murderers in the 1990s, homing in on several brain regions that seemed to be related to homicidal behaviors. However, as corresponding author on this new study Kent Kiehl tells New Atlas, much of this prior neuroimaging work commingled homicidal behavior with other psychiatric conditions such as schizophrenia or psychopathy.

"These early studies relied on murderers who had been found not guilty by reason of insanity (NGRI), and thus include effects of comorbid psychosis and organic brain injury alongside those effects specifically related to homicidal behavior," Kiehl tells us via email. "So yes, our study is novel in that we excluded men with psychosis and brain injury. We also studied nearly 1,000 total offenders in this paper. By far the largest study to date."

The research looked at structural MRI data from subjects categorized into three groups: 203 "homicidal" subjects (including self-reported homicide offenses and explicit attempted murder convicts), 475 violent but non-homicidal subjects (including assault, domestic violence, and other cases consisting of serious bodily harm), and 130 minimally violent subjects (drug possession, prostitution and other crimes resulting in no serious injury to others).

The results strikingly found a number of gray matter differences in the brains of those subjects who committed a homicide, compared to the other two groups. In fact, the researchers suggest there was little difference between the violent but non-homicidal subjects and the minimally violent subjects, implying there are significant gray matter reductions in several brain areas that particularly distinguish homicide offenders from other kinds of criminals.

"The orbital frontal cortex and anterior temporal lobes showed the largest effect sizes; that is, men who committed homicide had less gray matter in these regions than other violent or nonviolent offenders," Kiehl tells us.

These results are arguably rather strange considering the heterogeneous nature of homicide. The study does note it only included serious homicide offenses in the homicide cohort. So accomplices to murder were not included, nor were possible accidental death cases. However, this still strangely mashes up over 200 homicide offenders into a single group. Intent, for example, is not clearly accounted for here, so the study implies little neurological difference between a homicide that resulted from an aggravated assault gone wrong and a more violent, intentional act of murder.

The study does clearly note, "it should not be mistaken for the ability to identify individual homicide offenders using brain data alone, nor should this work be interpreted as predicting future homicidal behavior."

Although, directly questioning Kiehl on this point, he suggests predicting future homicidal behavior from brain data is a reasonable future outcome from this kind of work … and the more data that can be gathered, the more accurate these predictions may ultimately be.

"Yes, this is a first step towards using neuroscience to help predict who will commit homicidal behavior and identifying neuro-risk factors for homicidal behavior," Kiehl tells us. "Our future goals include following up large samples of high risk youth to see if the regions we have identified in this study do predict future homicidal behavior in those samples."

It is fair to be mildly unsettled at the ultimate implications of this research. Kiehl is gesturing to a degree of biological determinism here, suggesting there could be a specific brain "fingerprint" that identifies a person with the capacity to commit murder. Does this mean brain imaging could become major evidence in future murder trials? Or even more disturbing is the question of what we do with the knowledge that there may be an identifiable kind of homicidal brain?

Neurocriminologist Adrian Raine suggests these kinds of criminal brain fingerprints don't necessarily predict future antisocial behaviors but instead imply a certain greater propensity for these kinds of behaviors. When asked in 2013 whether he would be comfortable subjecting his own children to a brain scan that could preemptively assess violent tendencies, he likens the hypothetical process to a kind of public health crime prevention program, where behaviors may be identified and changed at young ages before they develop.

"If there was the opportunity for screening at school or through a GP programme, would I do it? Well, if my kids had problems, as a parent I would want to know about them and I would want to know how I might deal with them," Raine told The Guardian in 2013. "If you brought in such things as emotion regulation and impulse control, which we know are risk factors for behavior, then to me, as a parent, I would sort of want to know what could be done to help with those."

Kiehl is perhaps a little more reticent to hypothesize on the social or cultural outcomes of his line of research. It may be evasive, or merely the classically cold, blinkered vision of a scientist, and Kiehl accepts the potential directions his research could lead in but simply asserts more work is needed before any confident conclusions can be made.

"This study definitely points in the direction of developing a brain 'fingerprint' for homicidal behavior, but our results need to be replicated and we need to conduct longitudinal studies in order to more fully address this critical issue," Kiehl concludes.

The new study was published in the journal Brain Imaging and Behavior .

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COMMENTS

How the brains of murderers look different
Examining brain scans of more than 800 incarcerated men, new research co-authored by a leading University of Chicago neuroscientist found
What can neuroscience tell us about the mind of a serial killer?
This showed that criminal psychopaths had decreased connectivity between the amygdala—a brain region that processes negative stimuli and those
7 Lessons from Murderers' Brain Scans
According to research in The Journal of Neuroscience, the rate of aggression and violence after a TBI ranges from 35%-90%. The brain scans
Murderous Minds: Can We See the Mark of Cain?
The answer, we think, lies in the occipital cortex, which was more activated in murderers than in controls. The murderers seem to have recruited this visual
Aberrant brain gray matter in murderers
A large and growing body of research highlights the roles of frontal, temporal, limbic, and paralimbic brain circuits for promoting and regulating
The Difference Is In the Brain
This is important because research shows that an average person doesn't think the same as a serial killer does. The serial killer's brain has a.
A Neuroscientist Uncovers A Dark Secret
For nearly 20 years, neuroscientist Jim Fallon has studied the brains of psychopaths. After learning that his ancestry included alleged
Can Genes And Brain Abnormalities Create Killers?
So he believes that the brains of serial killers operate differently. On brain scans, it looks like their orbital frontal cortex, which is right
How to spot a murderer's brain
In particular, the murderers' brains showed what appeared to be a significant reduction in the development of the prefrontal cortex, "the
Inside the head of a killer: Imaging study uncovers unique brain
This new research, based on brain imaging data from 808 incarcerated male adults, suggests the brains of individuals that have committed murder