Complex brain imaging is making waves in court

(10-16) 20:48 PDT -- Science and the American legal system historically have had a complicated relationship. While good science has driven solid law, junk science like eugenics and phrenology have influenced due process with often terrible consequences.

Over the past decade, researchers have made huge advances in neuroscience, developing brain-imaging techniques that show not just the structure of the brain but its inner workings. According to experts in a new field called neurolaw, the effect of these breakthroughs on the legal system could be revolutionary.

"The law is mainly about brains or, at least, the mind," said Stanford law Professor Hank Greely, one of the directors of the year-old MacArthur Foundation-funded Law and Neuroscience Project. "If my fist hits your chin, what, if anything, I was thinking is crucial. If I was in an epileptic fit, if I was thrown from a car when I hit you, you don't convict me of a crime. ... If I'm mad at you, we do."

The degree to which brain scans will be admissible in court remains unclear, but experts already are pointing to precedent-setting cases and warning that neuroscience could alter the law, creating new methods and new visual evidence to determine criminal intent and criminal responsibility.

Greely, 56, who directs both the law school's Center for Law and the Biosciences and the neuroethics program at the Stanford Center for Biomedical Ethics, has led the charge to make sure advances in neuroscientific research are applied cautiously to the legal realm.

"Neuroscience has some real potential to be used as important evidence in cases and give broader insights into the law," he said. "It also has the real potential to be misused. If it's applied too early, it can lead to bad results."

The law is as vulnerable to faulty cultural and scientific thinking as any other field, which is why Greely calls for vigilance in neuroscience. In the 20th century, eugenicists who sought to "improve" the American population by weeding out bad hereditary characteristics convinced courts to uphold bad policies like the sterilization of the mentally retarded. Phrenology, a quack science whereby the shape of people's skulls was thought to reveal their personality, was heralded by scientists and criminologists in the mid-19th century as way to predict criminal behavior.

The importance of fMRI

One technique in particular - functional magnetic resonance imaging (fMRI) - holds the greatest legal promise and peril. By placing a person's head in what is essentially a large magnet and asking questions, researchers can link active brain anatomy to different cognitive skills - reason, decision-making and logic and perhaps even locating the neural pathways for lying and addiction. As opposed to magnetic resonance imaging (MRI), which shows the brain's structure, fMRI charts how the brain functions and thereby relates more closely to thought and behavior.

The problem is that while scientists have become very good at collecting group brain data, individual fMRI scans are too idiosyncratic to be interpreted accurately.

"Some things we know how to detect on a scan. If your visual cortex is destroyed by a stroke, you won't be able to see. If your Broca's region is destroyed, you won't be able to talk," Greely said. "That's what makes (neuroimaging) such a tease - we've known a few of these (functions) for a long time, but for most behavior we just don't know what's going on in the brain."