Vanderbilt Law Review


John C. Bush

First Page



Polygraph tests rely on the hypothesis that a subject's body yields physiologically different symptoms if he or she is lying.' When a polygraph test is administered, a mechanical apparatus records the subject's physiological changes, and the polygrapher conducting the examination interprets the data. The techniques for measuring physiological changes vary in their foci, which may include respiration, blood pressure, cardiovascular function, and skin resistance. The polygraph apparatus records changes to one or more of these foci, and a technician, or polygrapher, then analyzes the results to conclude whether the subject has been truthful.

Polygraph results factor into choices ranging from indictment determinations to employment decisions. Between 1981 and 1997, the Pentagon conducted more than 400,000 polygraph examinations. Similarly, state law enforcement officers have conducted thousands of polygraph examinations. Even in the private sector, where federal law significantly limits private employers from requesting polygraph examinations, employee test results may lead to criminal liability.

While other segments of society use polygraph results, courts remain reluctant to admit them. Although only two federal circuits employ common law bans against polygraph evidence, district courts in every circuit consistently reject polygraph evidence. Similarly, many state courts have excluded polygraph evidence for all purposes.' Unfortunately, many of these courts can only exclude polygraph evidence by warping generic evidentiary rules to act as per se bans. This Note focuses on their misapplication of evidentiary rules.

Included in

Evidence Commons