Someday soon, judgments of guilt or innocence in a courtroom might be determined from a brain scan, scientists say.
Technologies for imaging the brain have advanced rapidly, to the point where it's possible to infer, for example, what object a person has stolen based on that person's neural activity. But how reliable is the science, and should it determine criminal fate? A panel of scientists and legal experts discussed these issues Saturday (June 1) at the World Science Festival, an annual celebration and exploration of science held here.
The panel discussion was based on an upcoming PBS documentary called "Brains on Trial with Alan Alda," expected to air in September, and moderated by Alda himself. [Watch a Replay of 'Brains on Trial' Discussion]
Guilt in the Brain
Functional magnetic resonance imaging (fMRI) is one promising technique for determining a person's guilt. The technique detects changes in blood flow that highlight which parts of the brain are active.
In a clip from the documentary, Alda participates in an fMRI experiment. He is told to "steal" an object -- either a ring or a watch -- from a drawer, without telling the researcher what he took. Alda undergoes an MRI scan where he is instructed to lie about what he stole. From that scan, the researcher correctly determines what Alda stole, because when he lied, the activity in part of his brain changed and gave him away.
Using brain scans, scientists can detect when a person is lying with 70 to 90 percent accuracy, said panelist Anthony Wagner, a psychologist and neuroscientist at Stanford University in Palo Alto, Calif.
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In other studies, a subject being scanned need only look at an image (of a crime scene, for instance), and their brain will light up in a certain way if the image is familiar, Wagner said. The problem with using fMRI scans as evidence of guilt is that the brain may show similar activity patterns if the subject simply imagines committing the crime.
Scanning the brain of an accused person also brings up concerns about the right to privacy. "What kinds of constitutional or other legal protections might a person have, which would preclude police from being able to give a suspect a brain scan?" said panelist Nita Farahany, a law professor at Duke University in Durham, N.C. "There's nothing clear-cut that would protect us against that kind of thing if we are a legitimate suspect of a crime," Farahany said.