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Lie detectors have been controversial since their introduction nearly a century ago. With scientific studies producing mixed results, the controversy shows no sign of abating. Their use in the workplace is restricted by both federal and state laws.

How a Polygraph Works

Polygraph technology is based on the certain involuntary physiological changes people tend to undergo when they are telling a lie. A polygraph examination uses between four and six sensors attached to the subject's body. The sensors are connected to a machine that monitors respiration, pulse rate, blood pressure and perspiration. Several control questions are asked in order to establish the subject's baseline measurements before the examiner moves on to the questions of interest. The polygraph machine records the physiological data and later, the examiner reads the report to find the telltale signs of deceit.