The Department opposes all attempts by defense counsel to admit polygraph evidence or to have an examiner appointed by the court to conduct a polygraph test. Government attorneys should refrain from seeking the admission of favorable examinations that may have been conducted during the investigatory stage for the following reasons.

Though certain physiological reactions such as a fast heartbeat, muscle contraction, and sweaty palms are believed to be associated with deception attempts, they do not, by themselves, indicate deceit. Anger, fear, anxiety, surprise, shame, embarrassment, and resentment can also produce these same physiological reactions. S. Rep. No. 284, 100th Cong., 2d Sess. 3-5 (1988). Moreover, an individual is less likely to produce these physiological reactions if he is assured that the results of the examination will not be disclosed without his approval. Given the present theoretical and practical deficiencies of polygraphs, the government takes the position that polygraph results should not be introduced into evidence at trial. On the other hand, in respect to its use as an investigatory tool, the Department recognizes that in certain situations, as in testing the reliability of an informer, a polygraph can be of some value. Department policy therefore supports the limited use of the polygraph during investigations. This limited use should be effectuated by using the trained examiners of the federal investigative agencies, primarily the FBI, in accordance with internal procedures formulated by the agencies. E.g., R. Ferguson, Polygraph Policy Model for Law Enforcement, FBI Law Enforcement Bulletin, pages 6-20 (June 1987). The case agent or prosecutor should make clear to the possible defendant or witness the limited purpose for which results are used and that the test results will be only one factor in making a prosecutive decision. If the subject is in custody, the test should be preceded by Miranda warnings. Subsequent admissions or confessions will then be admissible if the trial court determines that the statements were voluntary. Wyrick v. Fields, 459 U.S. 42 (1982); Keiper v. Cupp, 509 F.2d 238 (9th Cir. 1975).

[updated January 2020]