This mixed result — added punishment for the defendant’s being identified as a psychopath, tempered by empathy for his having a possible genetic predisposition — provides a good illustration of what legal researchers call the double-edged sword of biobehavioral evidence. On one hand, a biological predisposition suggests that a person is likely to be dangerous in the future and should get a longer sentence; on the other, it implies a lower threshold of responsibility. The evidence could cut either way, depending on the judge.
In other words, judges were more likely to be lenient, presumably because those with a genetic predisposition were less culpable or the offense. On the other hand, because a person was more predisposed to violence, they would likely reoffend, and a stiffer sentence was warranted.
So which consideration won out? The former.
In the study, three researchers at the University of Utah tracked down 181 state judges from 19 states who agreed to read a fictional case file and assign a sentence to an offender, “Jonathan Donahue,” convicted of beating a restaurant manager senseless with the butt of a gun. All of the judges learned in their files that Mr. Donahue had been identified as a psychopath based on a standard interview — that is, he had a history of aggressive acts without showing empathy.
The case files distributed to the judges were identical, except that half included testimony from a scientist described as “a neurobiologist and renowned expert on the causes of psychopathy,” who said that the defendant had inherited a gene linked to violent, aggressive behavior. This testimony described how the gene variant altered the development of brain areas that generate and manage emotion.
The account is an accurate description of one theory of how brain development may underlie aggressive behavior. Its applicability to any individual is unknown, however, given that many other factors could increase the likelihood of violence, researchers said.
The judges who read this testimony gave Mr. Donahue sentences that ranged from one to 41 years in prison, a number that varied with state guidelines. But the average was 13 years — a full year less than the average sentence issued by the judges who had not seen the testimony about genetics and the brain.
In interviews about their decisions, the judges said that a crime of aggravated battery like this one normally carried a sentence of nine years, on average, and 15 years if the defendant was identified as a psychopath, the researchers found.
“But then those who read about the biological mechanism subtracted a year, as if to say, ‘This guy is really dangerous and scary, and we should treat him as such, but the biological evidence suggests that we can’t hold him as responsible for the behavior,’ ” said James Tabery, an assistant professor of philosophy at Utah.
So what does this hold for sentencing? Does 18 USC 3553a permit consideration of genetic predispositions?