Criminals are well versed in the art of deception – and criminalists expect them to lie. Suspects are often prone to malingering – playing up mental and physical defects in order to shirk the responsibility of their actions. Psychiatrists will watch out for certain signals during interviews to alert them to a fake.

The criminal mind can produce some highly devious rouses – for example confessing to a lesser crime to mask a far more serious offence, which effectively provides a perpetrator with an alibi.

Nervousness is a common signal that a suspect may be lying. Fast or faltering speech, sweating or avoiding eye contact are all reliable warnings that a suspect may be lying. So too the way they sit, move and react to questioning. Any finger-tapping or fidgeting, slouching or slumping usually highlights self conscious body language.