Their Brains Made Them Do It

July 10, 2000 -- There's a criminal defense emerging that relies not on blaming society or psychosis -- or even the devil. There are researchers -- and now defense attorneys -- saying that having less gray matter than normal in a brain region called the prefrontal cortex may play a role in violent acts.

The prefrontal cortex is an area at the foremost outer portion of the brain, right behind the eyes. Researchers think that it plays a role in controlling emotions and behavior -- even violent behavior. In the brain, gray matter makes up the nerve cells, in essence the thinking part of the brain. The white matter in the brain links the cells together, allowing them to communicate.

While no one is keeping track of how often brain scans are being introduced as evidence in court, two recent murder cases have spotlighted this defense theory: that of Kip Kinkel, who is accused of murdering four people including his parents, and that of Cary Stayner, the motel handyman accused of murdering four people in Yosemite National Park.

Kinkel was found to have holes in his prefrontal cortex, and various reports say Stayner is scheduled to check the amount of his gray matter by undergoing a positron emission tomography (PET) brain scan, which is similar to magnetic resonance imaging (MRI).

One of the researchers at the forefront of this argument is Adrian Raine, MD, of the University of Southern California. Reporting in the February issue of the journal The Archives of General Psychiatry, Raine writes that people with antisocial personality disorder sweat less and do not experience an increase in their heart rate when under stress. Raine says unlike normal people, people with antisocial personality disorder are more likely than others to lie, be impulsive and irresponsible, lack remorse, and commit violence.

While many neurologists have long been aware of a strong link between damage to the prefrontal cortex and antisocial, psychopathic-like personality changes, Raine's study takes it one step further by taking people with lifelong antisocial tendencies and showing that they have damage to this part of the brain.

One researcher who doesn't buy it is Helen S. Mayberg, MD, professor of psychiatry and neurology at the Rotman Research Institute and the University of Toronto, both in Ontario, Canada. While she won't directly comment specifically on Raine's study, she tells WebMD the trend toward the use of PET brain scans -- or any similar test -- in the courtroom are moves led by defense attorneys and not by doctors.

"Anyone who is facing murder charges will be depressed when the PET scan is taken, and that [depression] might very well show up," during the test, she says. "But there isn't enough evidence to show what their brain looked like at the time of the crime. It's not scientific."