“Hey listen, I’m not a bad man. I’m sick, see. Sick. What do you call it? Psychopathic. You know. Personality disorder. The court, man, he says so! You’re not gonna hurt me, are you? Jesus! You can’t kill me!” – Johnny the Boy, Mad Max (1979)
In 2009, an Italian court reduced a murderer’s sentence by one year because doctors had identified a gene in the defendant’s DNA, called MAOA, that had been linked to violent behavior. The ruling was controversial and some scientists objected to the sentence reduction. “MAOA findings have been generally used in murder trials, sometimes to suggest diminished capacity of the defendant to premeditate his criminal behavior,” but most often to reduce a sentence, writes Paul Appelbaum, a psychiatrist at Columbia University, in an essay published today in Neuron. In the essay, Appelbaum explains that genetic evidence demonstrating a defendant’s predisposition for antisocial behavior or mental illness is showing up in courtrooms at an ever-quickening pace. And that pace, he warns, might be outrunning the legal system’s ability to interpret it.
“Premature introduction of genetic evidence in court carries a number of risks,” said Appelbaum in an email to The Verge. “The most obvious is that the purported associations [between genetics and behavior] are not real and will be disproved over time.” But even the most replicated and widely accepted findings, he said, can be misinterpreted by judges and jurors