Science in the courtroom

San Diego

The AAAS meeting in San Diego has been something of a blur. The highlight so far has been a session called The Brain on Trial, which was an attempt to reproduce the courtroom discussion surrounding the admissibility of evidence from an MRI scan of the brain in a court case. Judge Luis A. Rodriguez, from the Superior Court of California in the County of Orange, presided over the session. There were lawyers for the prosecution and the defense, and two expert witnesses in neuroscience.

This session was the AAAS at its best. Well thought out, and well planned. The scenario was a trial in to the murder of a woman called Jane Owens by a former lover Will Johnson. Will Johnson is on trial for first degree murder, however the defense would like to argue that he has a lesion on his brain that makes him incapable of forming an intent to kill--and therefore could not have planned to murder Jane Owens.

Theoretically, lesions of the type that Mr Johnson has (in the cortex, which is the planning region of the brain) could lead to a failure to form an intent to kill, it equally might leave him completely or mostly normal. In addition, one would expect that such a failure in ability to plan would be reflected in his everyday life as well, from getting up in the morning to put on his pants, to making his dinner at night.

The difficulty that arises with the evidence of a lesion that no scientific data exist that would help a juror decide how likely this lesion was a factor in the murder. Indeed, many people have lesions in their brain and walk around entirely unaware of them.

The prosecution didn't want it admitted in evidence, and argued it would be likely to confuse, mislead and take a great deal of court time to discuss. The defense wanted it included, arguing it was evidence. The scientific experts provided different views of the evidence, according to which side they represented, but both would agree that the lesion was far from proof that Mr Johnson could not have formed an intent to kill.

The judge took the not-unreasonable view that it was up to the jury to decide. But of course the prosecution then used this evidence to suggest there was "reasonable doubt". It was fascinating to watch, and the audience voting (as jurors) suggested that such evidence would sway them from a conviction for first-degree murder.

This was a hypothetical example, and any court case would (one would hope) not end up hanging on a dodgy MRI scan (and with an absence of psychological evidence of past or current mental problems). But the entire session was a graphic window into how science can be used in the courtroom.

Whether or not scientists believe that their research is reliable evidence of anything, it may well appear in the courtroom.