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Is the polygraph really a lie detector?

On Behalf of | Oct 22, 2020 | Criminal Defense

While movies and TV shows have portrayed the polygraph as a valuable tool for court cases, the polygraph is actually a controversial invention that can’t be used as evidence in the courtroom. The polygraph works by measuring the individual’s breathing rate, heart rate and perspiration. Theoretically, the person’s heart and breathing rates will skyrocket when they tell a lie, as well as their amount of perspiration.

What the lie detector test is truly detecting

During the process, the authority asks the subject multiple questions about the court case as well as control questions to gauge their levels of anxiety. However, as the inventor of the polygraph himself has pointed out, the polygraph doesn’t actually detect lies. It simply detects an individual’s rate of stress, which can change for a number of reasons. As a result, the polygraph test can produce false positives.

While the polygraph is still used in the United States, the invention is still controversial. Many psychologists, scientists and police officers question whether the results are legitimate. Some say that a polygraph test should never be used in criminal defense trials. The Supreme Court ruled in 1998 that the results should never be presented as hard evidence of anything.

A controversial test

Only 23 states still allow the polygraph test to be used in trials. Some people claim that authorities can use a polygraph to bully people into confessing a crime that they didn’t actually commit. However, the American Polygraph Association claims that the tool has a nearly-universal success rate. While the invention has seen numerous changes and modifications over the years, many people still question its reliability.

When the machine was first invented decades ago, it was used as evidence in a trial, which secured a conviction for the person who was accused. However, the inventor of the polygraph repeatedly insisted that the machine detected stress–not lies. Despite this, the polygraph is still used in court cases and job applications.

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