Barbara Bradley Hagerty at NPR:
Kent Kiehl has studied hundreds of psychopaths. Kiehl is one of the world's leading investigators of psychopathy and a professor at the University of New Mexico. He says he can often see it in their eyes: There's an intensity in their stare, as if they're trying to pick up signals on how to respond. But the eyes are not an element of psychopathy, just a clue.
Officially, Kiehl scores their pathology on the Hare Psychopathy Checklist, which measures traits such as the inability to feel empathy or remorse, pathological lying, or impulsivity.
“The scores range from zero to 40,” Kiehl explains in his sunny office overlooking a golf course. “The average person in the community, a male, will score about 4 or 5. Your average inmate will score about 22. An individual with psychopathy is typically described as 30 or above. Brian scored 38.5 basically. He was in the 99th percentile.”
“Brian” is Brian Dugan, a man who is serving two life sentences for rape and murder in Chicago. Last July, Dugan pleaded guilty to raping and murdering 10-year-old Jeanine Nicarico in 1983, and he was put on trial to determine whether he should be executed. Kiehl was hired by the defense to do a psychiatric evaluation.
More here.