Kent Kiehl, a prominent neuroscientist hired to study an admitted murderer named Brian Dugan, had already been under cross-examination in the hushed, wood-paneled suburban Chicago courtroom for more than an hour when a brain diagram, hatched with X’s, was projected on a screen. The X’s marked areas where Kiehl had discovered abnormally low grey matter density in Dugan’s brain. In a curious meeting of law and neuroscience, those X’s would help jurors decide whether he should be executed or sentenced to life in prison. Did the way Dugan’s brain had developed leave him spring-loaded for violence? Or had he chosen freely when he abducted, raped and killed a 10-year-old girl in 1983?
Defense attorneys had brought in Kiehl and other experts to prove that Dugan was a psychopath incapable of experiencing normal emotions like remorse, in hopes the jury could be persuaded to sentence him to life in prison, rather than death.
Kiehl has interviewed and used new technologies to scan the brains of more imprisoned criminals than anyone else in the world. Here, he was asking jurors to accept that the brains of some criminals are simply different from the norm and that those differences should be considered during sentencing. “There are abnormalities in his brain function,” the tall, broad-shouldered Kiehl told the jury. Psychopaths make choices, he acknowledged, but “those choices are not necessarily informed by emotion in the same way ours are.”
The hearing last fall marked the first tim...