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Polygraph tests are `lie detector tests`. These tests use physiological markers in order to gauge the veracity of statements from those who take the tests. For example, blood pressure, pulse, respiration and skin conductivity responses are measured during the process of the polygraph test, in order to ascertain truth or deception. Created in 1921, by a USC Berkeley student, John Augustus Larson and a police officer from Berkeley, California, the polygraph test is considered one of the most impressive inventions of this century.

Polygraphs may or may not be admissible in court, although they are considered effective interrogation tools, regardless of whether or not they are admissible in a court of law. In terms of tools that may be used during police investigations, these lie detector tests often plenty of benefits, which is why they are so widely used.

Polygraphs have their proponents and critics. The National Academies of Science proved that polygraph testing did help investigators to tell truth from lies. However, results from polygraphs were not proven to be one hundred percent accurate. Some believe that it is possible to “trick” polygraphs, via drugs that are used in order to minimize physical responses, or by sociopaths who don’t exhibit the usual physiological markers when they lie (due to lack of guilt or empathy). Nonetheless, many a suspect has refused to take a lie detector test, because the test might incriminate them.

How Polygraphs are Used?

In certain nations, polygraphs are utilized in order to give police investigators the tools to solve crimes. For example, the CIA and FBI use these tests extensively, in order to narrow down lists of suspects. A suspect who passes a polygraph “with flying colors” may be excluded from further scrutiny, while someone who fails a polygraph may become a “person of interest” who is a prime suspect.

Law enforcement staff members are generally very strong proponents of polygraphs, despite the fact that they can’t use polygraph results in court. As a diagnostic, investigative tool, polygraphs are very sensitive instruments which may point law enforcement agents in the right direction (in terms of trying to arrest guilty parties). Within government agencies that use polygraphs, lie detector tests are also known as psychophysiological detection of deception (PDD) tests.

Polygraphs are Very Sensitive

According to the American Polygraph Association, this type of test offers an accuracy rate of 85 to 95 percent. Some studies from other governing bodies show even higher accuracy rates (of above 95 percent). When compared with other investigative methods, such as handwriting analysis, eyewitness reports and fingerprints, polygraphs offer better accuracy than witnesses, while providing less accuracy than fingerprints. The accuracy of handwriting versus polygraphs is almost the same.

Polygraphs work Due to their Sensors

These types of lie detector tests usually feature four, five or six sensors, which are connected to the person who is taking the test. Standard variables are then measured, including pulse, blood pressure, breathing rate and amount of perspiration. However, certain machines also measure movements in the arms and legs.