Brain scans have been used, perhaps for the first time in the US, as evidence in the sentencing stage of a murder trial. The defence for an Illinois man convicted of the rape and murder of a 10-year-old girl has used fMRI scans to argue that he should not be given the death penalty because of a brain disorder.

Brian Dugan pleaded guilty in July although the crime happened in 1983. Prosecutors sought the death penalty even though Dugan was already serving two life sentences for two other murders.

The defence argued that Dugan's psychopathy should be treated as a mitigating factor as it impaired his ability to control his behaviour. A University of Mexico at Albuquerque neuroscientist, Kent Kiehl, said that Dugan exhibited a plethora of the characteristics associated with psychopathy, including impulsivity, lack of remorse, antisocial behaviour, and that in a diagnostic checklist for psychopathy, Dugan scored 37 out of 40 points, placing him in the 99.5^th percentile.

Kiehl served as an expert witness to the defence, testifying that Dugan displayed characteristics similar to those he and others had observed in other psychopaths. However, Kiehl did not state that Dugan committed the crimes as a result of the brain abnormality. Kiehl said that "It's just one piece of evidence that his brain is different."

A New York University psychiatrist, Jonathan Brodie, conversely testified for the prosecution, stating that "I said the scans are of wonderful technical quality, but so what? They're not relevant here. Using an fMRI scan done in September of 2009… to indicate a thought process that was going on in 1983 could hardly be more silly."

Steve Greenberg, the lead defence lawyer, said that a 10-hour deliberation by the jury shows that the fMRI scans were at least influential in reaching a verdict in this particular case. "This guy was guilty of raping and killing little girls," said Greenberg. "Without the brain imaging stuff the jury would have been back in an hour." ~ Science, Nov 23