The brain, Your Honor, will take the witness stand

Every courtroom is a laboratory of human nature, where jurists clinically question our memory, behavior, sanity and sense of responsibility. Exploring the anatomy of justice, though, researchers have started taking testimony from the brain itself to better understand the origins of a fair verdict.

No one really knows how millions of microscopic brain cells can weigh objective legal notions of right and wrong. But last month, researchers at Vanderbilt University for the first time identified distinctive strands of neural tissue active when, like a judge or juror, we think about crime and punishment. In an experiment at the frontier of law and philosophy, the researchers used a brain scanner to examine the impartial judgments at the heart of our legal system, recording how brain cells behave when assessing criminal responsibility and meting out sentences.

"We take decision-making for granted, like breathing," says Vanderbilt law professor Owen Jones, who conducted the experiment with Vanderbilt neuroscientists Rene Marois and Joshua Buckholtz. "If you want a world in which judicial and jury decisions are fair, unbiased, sensible and reasonable, then we ought to understand a little bit about how it actually happens."

As a first step, they measured how our brain cells behave as we decide whether to punish someone accused of a crime when we have no personal stake in enforcement. The researchers tested 16 volunteers in a functional magnetic resonance imaging machine. The fMRI monitored the blood flow and oxygen demand associated with neural activity as each subject made two distinct legal judgments about blame and punishment in 50 hypothetical scenarios ranging from simple theft of a music CD to rape and murder.

No one part of the brain stands in judgment of others, they found. Instead, at least two areas of the brain assess guilt and assign an appropriate penalty. An area associated with analytical reasoning, called the right dorsolateral prefrontal cortex, became very active, they reported. But the decision process also electrified emotional circuits.

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