"One may sometimes tell a lie, but the grimace that accompanies it tells the truth."
Friedrich Nietzsche, German philosopher
Some lies roll off the tongue all too easily, while others can put the body under noticeable stress, inducing sweating palms, nervous twitches, contorted voices, and pounding heartbeats. Thanks to John Augustus Larson (1892-1983), signals such as these can also help to incriminate the sneakiest of liars.
Larson, a medical student at the University of California, invented the polygraph in 1921 and, In doing so, introduced one of the most contentious tools ever brought to the police officer's locker. Larson's lie detector worked by continuously and simultaneously monitoring physical responses such as changes to blood pressure, pulse rate, and respiration. Unfortunately, there is no known lie hormone that is secreted during acts of deception, and as the responses under surveillance can be triggered by any stressful situation or indeed be suppressed by any cunning criminal, there will always be question marks over the polygraph's credibility.
Despite the doubts, the lie detector is seen as one of the greatest inventions of all time, used most effectively in the earlier stages of an investigation when prime suspects need to be identified, or in civil investigations, which carry less severe penalties.
