Lie Detector Law and Legal Definition

Lie detector is an instrument that monitors a person's physiological reactions. As the name states, these machines does not detect whether what a person says is true or not. Instead, it detects any deceptive behavior displayed. Lie detector is originally called polygraph. A polygraph instrument is a combination of medical devices used to monitor changes occurring in the body. When a person is questioned about a certain incident, his/her heart rate, blood pressure, respiratory rate and electro-dermal activity such as sweatiness of the fingers are compared to the normal levels. Any fluctuation would indicate that s/he is being deceptive.