A suspect’s mental state can have an enormous influence on the direction of the trial. If they are deemed unfit for trial, a suspect can be acquitted. There are a number of psychometric tests which are designed to analyse the brain and determine mental capacity.

IQ tests help professionals evaluate a suspect’s intelligence and thought processes, while projective testing helps them unravel the mysteries of their personality. These examinations help forensic psychiatrists gain an insight into the subject’s obsessions, which may have an influence on their behaviour. The most famous is the Rorschach test – where the patient describes a series of ink splotches.

Obviously, it’s imperative that the forensic psychiatrists get it right as misdiagnosis could jeopardise the entire trail. However, it’s not quite so simple - for a start, determining insanity only lies with the medical profession up to a point. Psychiatrists can only advise on their findings. The final say as to whether a suspect is insane and therefore unfit for trial, lies with the judge and jury.