A polygraph machine records the body's involuntary responses to an examiner's questions in order to ascertain deceptive behavior. The test measures physiological data from three or more systems of the human body-generally the respiratory, cardiovascular, and sweat gland systems-but not the voice. There are other tests that test the voice for deception.
"Polygraph “means literally "many writings," referring to the method of recording several physiological activities at the same time. William M. Marston invented the first lie detector in 1917. Marston claimed he could reveal verbal deception by observing levels of systolic blood pressure. However, in 1923, the D.C. Court of Appeals stated that there was not enough scientific evidence to support Matston's lie detector machine. Roughly a century later, Leonarde Keeler invented a machine and school for examiners that paved the way for the modern use of polygraph testing, especially in the legal realm.
Polygraph testing is mainly done for law enforcement, judicial and