Polygraphs may say the innocent are lying

Polygraphs do not always accurately predict whether someone is telling the truth or not. This is according to Chartered Psychologist Professor Chris French, who has been looking at British Psychological Society research into the effectiveness of these pieces of equipment, often referred to as lie detectors.

Writing in the Guardian, Professor French explained the 2004 Society study revealed that while this technique correctly identifies 85 per cent of guilty people, between 12 per cent and 47 per cent of individuals are judged to be lying when they are in-fact innocent.

Mr French was speaking after the government's announcement that it may make polygraph testing mandatory for serious sex offenders when they re-enter society following a stint behind bars.

He stated that "innocent people may be more aroused by the relevant questions than the control questions for a variety reasons", giving the example that a person wrongly accused of something illegal may see their results impacted by feelings of shame for other behaviour conducted around the same time.