Robbie Gonzalez in Wired:

Courtroom-TAOn July 1, 2013, Amos Joseph Wells III went to his pregnant girlfriend's home in Fort Worth, Texas and shot her multiple times in the head and stomach. He then killed her mother and her 10-year-old brother. Wells surrendered voluntarily within hours, and in a tearful jailhouse interview told reporters, "There's no explanation that I could give anyone, or anybody could give anyone, to try to make it seem right, or make it seem rational, to make everybody understand."

Heinous crimes tend to defy comprehension, but some researchers believe neuroscience and genetics could help explain why certain people commit such atrocities. Meanwhile, lawyers are introducing so-called neurobiological evidence into court more than ever.

Take Wells, for instance. His lawyers called on Pietro Pietrini—director of the IMT School for Advanced Studies in Lucca, Italy and an expert on the neurobiological correlates of antisocial behavior—to testify at their client's trial last year. “Wells had several abnormalities in the frontal regions of his brain, plus a very bad genetic profile," says Pietrini. Scans of the defendant's brain showed abnormally low neuronal activity in his frontal lobe, a condition associated with increased risk of reactive, aggressive, and violent behavior.

More here.