Why do some people murder? Is it in their blood? Maybe so, according to scientific studies that suggest that there is a genetic basis for violent behaviors:
They've tested some 30 criminal defendants, most of whom were charged with murder. They were looking for a particular variant of the MAO-A gene — also known as the warrior gene because it has been associated with violence. Bernet says they found that [the defendant] Waldroup has the high-risk version of the gene.
"His genetic makeup, combined with his history of child abuse, together created a vulnerability that he would be a violent adult," Bernet explains.
Over the fierce opposition of prosecutors, the judge allowed Bernet to testify in court that these two factors help explain why Waldroup snapped that murderous night.
"We didn't say these things made him become violent, but they certainly constituted a risk factor or a vulnerability," Bernet says.
Bernet cited scientific studies over the past decade that found that the combination of the high-risk gene and child abuse increases one's chances of being convicted of a violent offense by more than 400 percent. He notes that other studies have not found a connection between the MAO-A gene and violence — but he told the jury that he felt the genes and childhood abuse were a dangerous cocktail.
"A person doesn't choose to have this particular gene or this particular genetic makeup," Bernet says. "A person doesn't choose to be abused as a child. So I think that should be taken into consideration when we're talking about criminal responsibility."
Does that make a person less culpable of his own actions? What do you think of the "my genes made me do it" defense?