The mind of a killer

A neurologist who studies murderers' brains talks about factors that make someone kill, the difficulty of predicting violence and why most murderers can never be rehabilitated.

By Suzy Hansen

July 27, 2001 | In the past 25 years, Jonathan Pincus, chief of neurology at the Veterans Administration Hospital in Washington and a professor at Georgetown University School of Medicine, has sat across the room from 150 murderers. He has questioned them about their childhood, administered I.Q. tests and performed neurological examinations. Pincus met with 15-year-old Kip Kinkel after he killed his parents and opened fire on a school in Springfield, Ore. He spent hours with Russell Weston, the man who shot two guards inside the U.S. Capitol. And he interviewed a charming white-collar professional named Ted Bundy after he mutilated and murdered as many as 50 women.

All of these people, young and old, white and minority, middle class and poor, shared a handful of characteristics that, in Pincus' estimation, transformed them from average citizens to coldblooded killers. In "Base Instincts: What Makes Killers Kill," Pincus presents his research -- much of which deals with scientific information about the frontal lobes of the brain -- in a nimble, absorbing and highly entertaining way. (His stories will have you checking the lock on your front door several times before you turn out the lights.) Although Pincus does not treat his subjects sympathetically, he also knows that to cast them off as evil, morally debased monsters limits our understanding of the ingredients that somehow get thrown together to create a killer.

Pincus spoke with Salon from his office in Washington.

According to your book, three things intersect to create a killer: mental illness, neurological damage and child abuse. Are all three always there?

Two-thirds of murderers have all three factors, and the others have two of the three. It's pretty clear that mental illness is not enough to cause violence because most people who are mentally ill are not violent. It's also evident that neurological damage is not enough to cause violence because the vast majority of people who are neurologically impaired are not violent. And it's clear that the experience of horrendous child abuse is not enough to cause violence because most people who are abused that way are not violent. Yet, most violent people have these three factors, or two of the three. That's an indisputable fact.

The theory that explains it is that abuse sets up an impulse toward violence that a good brain can control. If you get the abuse and the neurological damage and mental illness, then violent impulses are not easy to check. That's why they are expressed under stress or at times of jealousy or anger.

Have other doctors, sociologists or psychiatrists pinpointed similar causes?

When people have looked, they have found similar causes. You have to do a very thorough study. It takes me three to four hours with somebody -- that's the time I spend with the individual, examining him, questioning him and talking to him -- and it takes a psychiatrist at least double that time. And that doesn't count the review of medical, police and school records that are also available for examination.

How do you determine that a person is neurologically impaired?

There are many neuropsychological tests, just as there are many kinds of blood tests. I do a number of tests of cortical function -- the cortex is the part of the brain that you think with -- and most of my tests measure motor and sensory function. For example, I have the patient follow my horizontally moving finger with his eyes to see if his visual tracking is smooth. If it's not smooth, it indicates that the frontal eye fields are not working properly.

What about an I.Q. test?

People don't realize that an I.Q. test is not a test of all the parts of the brain. It's a pretty good screening tool for the back parts of the brain, but not a very good one for the front of the brain. That's the place where most of the neurological deficits in murderers reside -- in the frontal lobe.

Were most of these people born with this neurological damage, or did their environment contribute to it?

It's very difficult to say in most cases. In some of them, where there is a history of maternal drinking and drug use and there are physical characteristics associated with the fetal alcohol effect, it's reasonable to think that the child was born with it. If someone's head circumference is more than two standard deviations below the mean, then you can assume that this damage occurred, if not prenatally, then shortly after birth.

But most of the time there are many factors that could have played a role in the neurological dysfunction, for example, head injury -- the experience of being physically abused by being beaten in the head. And then there are automobile accidents, a history of meningitis, a history of encephalitis, a history of unconsciousness, seizures, epilepsy and drug use. It's very hard to know which of those factors was the most important one in damaging the brain, which part of the brain it damaged and when that damage was sustained.

Next page: The making of a pedophile