(This article appeared in the 7 December, 2006 issue of Nature.)

Can brain scans of a racist, liar or psychopath accurately tell whether that person will persecute, fib or kill? No, say experts in the ethics of neuroscience, who are increasingly concerned that such images will be used to make dangerous legal or social judgements about people’s behaviour. They say it is time for scientists, lawyers and philosophers to speak up about the limitations of such techniques.

“Lawyers want to know ‘Can I put somebody on the scanner and tell if they’re racist?’” says Elizabeth Phelps, a psychologist and neuroscientist at New York University who has studied the brain’s response to race. “We as 
a group of scientists have to be 
able to say that we can’t make that distinction.” Phelps spoke at a panel discussion on the emerging field of neuroethics held in New York last week.