Jeffrey Dahmer’s Brain: Inside the Mind of a Serial Killer
Decades after the grisly murders, what can neuroscience reveal about evil and the nature of free will?
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In 1995, serial killer Jeffrey Dahmer was on trial. Or at least his brain was.
This trial was not to convict Dahmer of murdering and cannibalizing 17 mostly young Black men.
This trial would decide whether Dahmer’s brain should be donated to science or cremated.
His mom, Joyce Dahmer (Flint), wanted answers. Joyce requested that scientists study her son’s brain to determine if biological factors caused his violence.
His dad Lionel Dahmer wanted closure. Lionel wanted his son’s brain cremated and to put the saga behind him.
On December 13, 1995, a judge ordered Dahmer’s brain cremated, forever preventing scientists from revealing its secrets. But decades later, neuroscientists have studied the criminal mind and found commonalities.
This is your brain on murder
In 2019, University of Chicago neuroscientists scanned the brains of 800 violent criminals to answer one pivotal question — is a killer’s brain different from other brains?
Unlike previous studies, the researchers used only incarcerated criminals and eliminated any brains with mental illnesses or traumatic brain injuries.
The results were surprising. Researchers found that criminal brains had reduced grey matter with decreased activity in the brain’s orbitofrontal cortex and anterior temporal lobes — the areas that control emotional processing and social cognition. Basically, the brain areas that regulate emotions and empathy toward others were damaged or weakened.
Most interestingly, the researchers did not find differences in the brains of ALL violent criminals. They only found differences in those who committed homicides. So, the brain of a murderer looks very different from that of a mugger.
These studies still had their limitations. Researchers were only taking one snapshot in time. More informative data would determine when these brain changes occurred. Were the criminals born this way, or did they develop a murderer’s brain over time?
Unfortunately, one can start with a healthy brain and end with an injury that causes irreparable damage to cognitive reasoning.
The link between brain trauma and violence
The list of serial killers who suffered childhood brain injuries is long: Ed Gein, Jerry Brudos, Gary Heidnik, Richard Ramirez, Henry Lee Lucas, Alexander Pichushkin, David Berkowitz, Bobby Joe Long, Dennis Rader, Peter Sutcliffe, John Wayne Gacy, Albert Fish, and yes…Jeffrey Dahmer.
Dahmer endured a double hernia surgery and a brain injury when he was a boy. Dahmer’s father claimed these traumas caused his son to withdraw and exhibit deviant behavior.
His father also claimed that Jeffrey suffered sexual abuse when he was eight. (26% of serial killers were sexually abused as children.)
Like most serial killers, Dahmer’s violence started with animals. He cut up roadkill and played with their bones. As a teen, Dahmer drank heavily and further withdrew.
He committed his first murder in 1978. He was only eighteen years old.
But how much of Dahmer’s psychological and physical trauma led to his crimes?
According to the latest research, traumatic brain injuries (TBIs) account for increased aggression and violence, ranging from 35%-90%. Other studies have been less conclusive. A 2014 study found that 20% of mass murder cases were linked to traumatic brain injuries.
Phineas Gage is a classic case of how a brain injury causes an aggressive personality. On September 13, 1848, a tamping rod tore through Gage’s head, damaging his left frontal lobe. He survived the injury, but his personality changed afterward. According to his friends, Gage went from being a calm, even-keeled guy to “fitful, irreverent, indulging at times in the grossest profanity.”
Of course, Gage didn’t kill and eat multiple people. There must be some accountability for extreme violence. Or is there?
Is there a serial killer gene?
Is a serial killer born or made? That is the question scientists have grappled with when studying the genotype of serial killers.
Several genes have been linked to more aggression, but the most studied is the MAOA gene — known as the “warrior gene.” MAOA plays a key role in the breakdown of dopamine and serotonin. Dopamine is the neurotransmitter that controls the reward pathways in our brain, while serotonin helps regulate mood.
Research on the MAOA gene has been controversial. First, one-third of the population carries low levels or defects in the MAOA gene. And clearly, we would have a problem if one-third of humans became serial killers. (Serial killers commit only 1% of murders in the U.S.)
A flaw in the MAOA gene has also been linked to a mutation in the X chromosome. Since men have only one X chromosome, researchers have posited that this is why more men are serial killers. (Although female serial killers certainly exist.)
Of course, genes are not a roadmap to violent behavior. Environment plays a role too. For example, having the gene that increases the risk of depression does not mean you will get depression. Genes influence behavior, but they do not determine it.
How much of evil is free will?
Any discussion on why humans kill inevitably stirs the debate on free will. How much moral outrage should we feel if a criminal’s brain chemistry prevents him from controlling his impulses?
When it comes to free will, even simple decisions such as moving are predetermined. According to recent studies, activity in the brain’s motor cortex can be detected 300 milliseconds before a person decides to move. Think about that. Our decisions are made before we are even aware there is a decision to be made.
Free will is a thorny subject for most. One of the most thought-provoking discussions regarding free will is from author and researcher Robert M. Sapolsky. (Sapolsky is currently working on a book titled Determined: The Science of Life Without Free Will.)
Sapolsky contends that free will is an illusion. He then posits that if humans could accept that free will is a myth, there would be less hate and violence.
I am not convinced. If society accepted free will as a myth, it would engender more hate, not less.
To prove my point, here’s a little personal background about how I became an award-winning author of thirteen books.
My parents were immigrants employed in a local factory. They worked hard, made sacrifices, and passed on their legacy of determination to me. I was a straight-A student who stayed out of trouble despite living in a crime-infested neighborhood. In my junior year of high school, I was awarded a four-year scholarship. I pursued publishing like a rabid Pitt Bull and got my first book deal after piles of rejection letters.
Or maybe that is not my story. Maybe my story is this…
My parents were both trust fund babies born into old money. They were also extremely good-looking and brilliant. They passed on their beauty, intelligence, and bank account to me. My father knew someone in publishing, pulled a few strings, and got me my first book deal.
Which narrative endears me to you more? (By the way, both stories contain truths and lies.)
People admire those who pull themselves up by their meritocratic bootstraps, make wise decisions, follow a moral code, and accomplish the American dream through gritty determination.
People envy those born into privilege — more favorable economics, the right skin color or gender, superior genetics, stable households, etc.
And if there is one thing I learned from Grandma Ella, it is this: Envy seeds hate.
Think about free will from another vantage point. If we are not responsible for our failings, we also are not responsible for our accomplishments. Suppose free will is a myth and all our status in society comes from environmental and biological factors. Why should one person have more than another?
I hope you can see how this thinking would fan the flames of hate and violence.
It would also put all the self-help bros out of business. If free will is an illusion, so is self-help. Any “self” cannot “help” their actions without free will.
We can hope the answer lies somewhere between accepting your lot in life and working to change it. Perhaps that is why stoicism has so much appeal. Its message revolves around the tenet that you cannot control your environment or events. You can only control your reaction to that environment and events.
You can even be born with the brain of a psychopath. But through the powers of neuroplasticity, your brain changes. It fires off the synapses for empathy, kindness, and tolerance. And that light becomes your reality.
Although Dahmer’s brain was destroyed, the brain of serial killer Ted Bundy was not. After Bundy’s execution for the murder of at least 30 women in 1989, scientists removed his brain and examined it.
Unfortunately, scientists found nothing abnormal in Bundy’s nefarious noggin.
If Bundy’s brain wasn’t unique, how much of Dahmer’s evil was caused by brain abnormalities?
Dahmer never denied the evil that fueled his grisly murders. According to a statement to CBS news, he said, “I hated no one. I knew I was sick or evil, or both.”
Sick or evil? Even Dahmer questioned if they were mutually exclusive. If a sick brain causes sicker evil, how culpable is the sick person?
It’s interesting to examine Mr. and Mrs. Dahmer’s differing objectives regarding their son’s brain. His mom sought a biological reason for her son’s turpitude, while his father attached environmental reasons (surgical trauma, brain injury, and sexual abuse) to Dahmer’s crimes.
It’s the old nature vs. nurture debate between two warring parents. But in this struggle between biology and backstory, the answer was probably both.
Some of the above appears in my book, They Lost Their Heads: What Happened to Washington’s Teeth, Einstein’s Brain, and Other Famous Body Parts, published by Bloomsbury Books® and found in all major bookstores.
Carlyn Beccia is an award-winning author and illustrator of 13 books. Subscribe to Conversations with Carlyn for free content every Wednesday, or become a paid subscriber to get the juicy stuff on Sundays.