The last defence.

The last resort of the defence in a murder trial may be to try to persuade the jury that the defendent was insane. A reconstruction of events surrounding two U.S. murder trials, shows how doctors attempt to assess the state of mind of the accused. The law demands a direct link between psychiatric disorder and the crime and psychiatrists are seldom willing to make an unequivocal statement in this matter. If Petscan images are used as evidence of brain disturbance, expert witnesses will be called to interpret them for the jury, who will then be the focus of scientific dispute over interpretations. Can we be satisfied with a system that leaves a lay jury to resolve scientific disputes?