The polygraph and other lie detection devices, such as the psychological stress evaluator and the voice stress analyzer, measure a subjects physiological processes in the context of the testing stimuli under the assumption that deception can be detected from such measurements. Since physiological processes vary from person to person under similar stimuli and are dependent on a host of variables, the lie detection procedure is not a scientifically valid nor reliable instrument. Even if the tests were 100-percent accurate, testing conditions and the motives of their sponsors are constitutionally questionable. The tests conducted by employers and criminal justice agencies intrude into areas where citizens have a reasonable expectation of privacy. In the context of criminal investigations, such tests may require subjects to incriminate themselves. Overall, lie detection procedures may violate constitutional protections from unreasonable searches and privacy intrusions, inhibit free speech, and violate the dignity of the human personality. 16 notes and 14 references.