Probity of the Polygraph (From Psychology of Evidence and Trial Procedure, P 95-123, 1985, Saul M Kassin and Lawrence S Wrightsman, eds. - See NCJ-99863)

• NCJ Number: 99867
• Author(s): D T Lykken
• Date Published: 1985
• Length: 29 pages
• Sale Source: Sage Publications, Inc
• Language: English
• Country: United States of America

Annotation

A discussion of research on the use of polygraphs focuses on the different types of polygraph tests, their accuracy, and jury responses to polygraph evidence.

Abstract

Polygraph evidence is admissible under stipulation in some jurisdictions and not admissible in others. At least two categories of tests and two categories of examiners exist. The control-question test is now the standard technique, other test forms exist as well. A recent literature survey revealed that no evidence exists regarding the validity of the preemployment screening test widely used by Federal security agencies. In addition, the psychological assumptions underlying the tests are implausible. Credible scientific evidence regarding validity exists only for the control-question test and indicates that it is wrong one-third of the time. Its accuracy in particular applications depends on the base rate of lying in the population being tested. As used by defense counsel, its accuracy may be less than 50 percent. Moreover, the test is also biased against innocent, truthful witnesses, who have more than a 40 percent chance of being inaccurately diagnosed as deceptive. The test is unavoidably subjective. It can also be undermined by guilty suspects using self-stimulation during control questions. Studies using mock juries have found that unrebutted polygraph evidence is influential with a majority of jurors. However, competent scientific rebuttal testimony can convince juries that the use of the polygraph indicates a weakness in the case. Notes and 46 references.