LONDON: Scientists’ growing understanding of how the brain works may in future change the way criminals are viewed by the law, but British experts are advising extreme caution for now on the use of lie detectors, brain scans and genetic data in court.
In a report published Tuesday by the U.K.’s national academy of science, the Royal Society, leading scientists and lawyers looked at the scope for neuroscientific evidence to “read minds” in a bid to find the truth or to explain why a person acted in a particularly violent or sadistic way.
Claims that murderers can be identified by imaging studies of their brains before committing the crime, or that there is a gene for psychopathy or for violent behavior, are “completely wide of the mark,” the experts said.
But they did suggest neuroimaging and behavioral genetics, together with existing techniques, may in future be used as part of risk assessments for determining how long a sentence someone should serve, or whether a prisoner should get parole.
“There’s no doubt neuroscience will provide some startling revelations about human behavior but we can’t be allowed to get ahead of ourselves,” said Nicholas Mackintosh, a professor of experimental psychology at Britain’s Cambridge University who chaired a Royal Society panel looking into the issue.
“Understanding how the brain works gives us an insight into the mental processes that underpin human behavior, and as the law is primarily concerned with regulating people’s behavior it makes sense that the one may influence the other at some point down the line.”
At a briefing about the report, Mackintosh said a growing number of defense lawyers in the United States and a few other countries were beginning to use neuroscientific evidence in criminal cases, particularly in cases involving murder and other violent crimes.
Roger Brownsword of King’s College London’s law school, who worked on the report, said the admissibility of such evidence should be properly scrutinised and any lawyers, judges and expert witnesses using it must fully explain its strengths and weaknesses.
“Clearly some neuroscientific evidence could be very prejudicial in a courtroom,” he told the briefing. “Juries could be very easily swayed by this. So ... the threshold for admissibility has got to be pretty high.”
British scientists published a study in 2009 which found that psychopaths who had committed serious crimes like murder and rape had faulty connections in their brains which show up on functional magnetic resonance imaging (fMRI) scans.
“To the extent that neuroimaging data suggests there are difference in the brains of psychopaths ... [we should ask] would brain imaging evidence be helpful?” Mackintosh said. “The answer is we have no idea because no has yet done the research, but it’s at least something worth thinking about.”
But he stressed that “having a psychopathic brain is not a general defense against any criminal charge, and that’s because it doesn’t absolutely force you to behave in a criminal way ... it merely increases the probability.”
Functional imaging experiments with students have also shown differences in brain activity when they are telling the truth and when they lie, Mackintosh’s panel said in its report.
But the experts warned that the use of fMRI in defence of suspects in serious criminal cases, or for lie detection among defendants or witnesses, is fraught with difficulties – including the fact that people can fairly easily be taught how to defeat lie detectors.