Nolo's Plain-English Law Dictionary

Lie Detector Test

The popular name for a polygraph, which tests a person's physiological response (for example, changes in blood pressure and respiration) to questions asked by a testing expert to judge whether the person is telling the truth. The test's reliability is a matter of ongoing controversy, and in most U.S. states polygraph test results are not admissible in court.
NOLO-web2:DRU1.6.12.2.20161011.41205