Lie detectors are popularly used by law enforcement as a tool for detecting deception. These tests are often referred to as polygraphs and are designed to measure physiological changes in a person’s response to questions. Source liedetectors.co.uk

During an examination, a polygraph examiner asks a subject a series of questions about a specific issue and records the subject’s reactions to those questions. These responses are then analyzed by the examiner to determine whether the subject is telling the truth or lying.

However, the ability to detect lies through a polygraph test is highly controversial. Despite its popularity, there is little scientific evidence that the polygraph can accurately identify a person’s truthfulness or that it helps a court in determining a defendant’s guilt.

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A polygraph is a device that measures several physiological indicators, including blood pressure, pulse, respiration and skin conductivity while a subject answers questions. It was first invented in 1921 by a California police officer and physiologist named John A. Larson.

Originally, the polygraph measured blood pressure but was later equipped to measure galvanic skin resistance in addition to blood pressure. This was a better way to detect deception as it allowed the examiner to differentiate between the physiological effects of fear or anxiety, which are commonly associated with lying, and those that may just be a result of a subject’s nervousness when undergoing questioning.

Despite its controversies, the polygraph remains widely used by law enforcement and employers as part of employee screening. Although federal and most state law bans employers from requiring employees to submit to such tests, some states allow exceptions for embezzlement concerns.