Lie detectors or Polygraphs, were invented in 1921 by John Augustus Larson in Berkeley, California. They record blood pressure, pulse, respiratory and skin conductivity. This results in many (poly) graphs. The fluctuations in these responses is meant to indicate nervousness which is supposed to correlate to untruthfulness. The person is attached to the machine and asked a series of yes or no questions. The responses are plotted and interpreted by an expert.
Polygraphs aren’t used in British criminal prosecutions. They are not admissible in court as evidence and have been widely debunked. It is easy to get wrong results because there are many reasons why a person may have a physiological response to being attached to a polygraph other than lying. They are used in America to assist with narrowing down suspects but are not admissible as evidence of lying. They are used in the US by some employers prior to hiring an employee.
There has been a recent tragedy in the UK as it appears that a man died by suicide shortly after not passing a polygraph test on The Jeremy Kyle Show. The TV show has now been cancelled but there could be many more families impacted by the erroneous results of polygraph tests on the show. Public belief in the validity of the polygraph possibly persists due to their use in film and TV where they appear to be infallible. Last night Channel 4’s Dispatches did a report on The Jeremy Kyle Show and it’s impact and covered the varacity of polygraphs in lie detection, it will be available on demand on All 4 for those in the UK.