Dr. Richard Hicks testifies during the trial of Jason Strickland, November 2008. Credit: Dave Roback / ASSOCIATED PRESS

A father and husband strangles his wife and drops her out of a window in a staged suicide. Most people would view this act as cold-blooded murder—but might it be the tragic result of an untreated brain cyst? Such a possibility frames The Brain Defense, Chicago author Kevin Davis‘s true-crime book, which explores the emerging role of brain science in the criminal justice system.

The above story is that of Herbert Weinstein, a well-to-do retiree with no criminal record who in 1991 admitted to killing his wife. Expert witnesses claimed that an orange-size subarachnoid cyst (nicknamed Spyder Cystkopf) pressing on Weinstein’s brain’s frontal lobe (the center for judgment and impulse control) motivated his uncharacteristic act of violence. This controversial defense became a hallmark of his trial, which was the first U.S. case where a judge allowed a brain scan to be admitted as exculpatory evidence, ushering in a new precedent for using brain imagery to contextualize criminal behavior.

Weinstein’s case is just the tip of the iceberg. From Phineas Gage—a 19th-century man who suffered personality changes after a rod was driven completely through his head, severing his frontal lobe—to David Alonso—a loving father who anomalously attacked his wife and daughter after a head injury—The Brain Defense probes the sundry crimes, cases, and punishments of brain-injured individuals.

“People who commit crimes need to be held accountable for their actions,” Davis says. “So you get to a crossroads: This person committed a crime. What’s their mental state? I was following my curiosity—the connection between our brains, our behavior, and how that affects personality. I began to question the legal implications of whether or not someone who’s injured is responsible for what they do. That’s the driving question behind the book.”

Davis is no stranger to crime writing. As a young newspaper reporter in Florida, he was assigned the crime beat and was immediately attracted to the social undertones and storytelling potential of crime. From there, he wrote his first book, The Wrong Man, published in 1996.

Much like his foray into crime writing, The Brain Defense‘s conception was fortuitous. After Congresswoman Gabby Giffords was shot in the head during an assassination attempt in 2011, Davis became interested in how someone with an extreme traumatic brain injury could bounce back. He dove into the complex world of neuroscience, its intersection with the law, and the brain’s effect on behavior. The book addresses the relevant ethical considerations that trail neuroscience into the legal sphere: For example, to what degree are offenders with brain damage culpable? How should treatment be weighed against punishment for such individuals?

The brain defense isn’t without controversy. While science has proven that certain brain abnormalities link to aberrant behavior, how and to what extent are still up for debate. The value of brain scans in the courtroom is questionable: you can’t point to a machine-made image as incontrovertible justification for criminal acts, Davis says. Instead, brain scans can be used to better understand the mind of the offender. In The Brain Defense, Davis cites a number of pioneering lawyers and scientists who use neuroscience not to excuse criminal behavior but to help offenders find the right place in criminal justice or rehabilitation systems. Yet some lawyers, scientists, and families of victims find this approach risky—after all, if Weinstein committed one act of unpredictable violence, brain injury-induced or not, isn’t it possible that he might do so again? A PET scan can’t say.

That’s in part why there are contextual factors to consider when evaluating someone’s brain. Take Ronnie Cordell, a young man with a horrifically abusive upbringing who killed a homeless man. One can’t ignore the fact that Cordell clearly never learned right from wrong and bore the emotional damage of lifelong stress and fear, Davis writes. Or consider Kris Parson, a veteran charged with domestic violence who suffered from PTSD, memory loss, and other disabling symptoms as a result of an untreated traumatic brain injury from a blast attack in Iraq. Here, his lawyers argued, was a person who needed treatment, not time in prison.

Davis also uses the cases of psychopaths, football players, alcoholics, and individuals throughout history to illustrate the manifold types and consequences of brain injury, emphasizing that there’s no prototype for brain abnormalities and criminal behavior. Still, neuroscientists have a lot more work to do, and Davis says he’ll continue to explore neuroscience and the law, perhaps in an upcoming book, he hints.

“The key to the brain defense is living in a world where we have compassion for each other,” Davis says. “Right now, I don’t feel that. We need to have people who are making our laws and running our country who have compassion. A system in which we seek to understand and not just blindly punish is going to depend on all of us. Compassion is not incompatible with people taking responsibility. People need to be held accountable for their actions, but to what extent?”  v