OVERVIEW

There have been a number of previous reviews of the validity of the polygraph and related techniques (e.g., Levey, 1988; U.S. Office of Technology Assessment, 1983; see also Lykken, 1981; Murphy, 1993), each of which has examined partially overlapping sets of studies, though it is unlikely that any review (including ours) covers every study done. What is remarkable, given the large body of relevant research, is that claims about the accuracy of the polygraph made today parallel those made throughout the history of the polygraph: practitioners have always claimed extremely high levels of accuracy, and these claims have rarely been reflected in empirical research. Levey’s (1988) analysis suggests that conclusions about the accuracy of the polygraph have not changed substantially since the earliest empirical assessments of this technique and that the prospects for improving accuracy have not brightened over many decades.

We used several methods to gather as many polygraph validation studies for review as possible (see Appendix G). Our search resulted in 217 research reports of 194 separate studies (some studies appeared in more than one report). The committee next determined which studies were of sufficient quality to include in our review. We agreed on six minimal criteria for further consideration:

  1. documentation of examination procedures sufficient to allow a basic replication;

  2. independently determined truth;

  3. inclusion of both guilty and innocent individuals as determined by truth criteria;

  4. sufficient information for quantitative estimation of accuracy;

  5. polygraph scoring conducted blind to information about truth; and,

  6. in experimental studies, appropriate assignment to experimental groups germane to estimating accuracy (mainly, guilt and innocence).

Our detailed review by staff selected 102 studies that deserved further examination by the committee because they met all the criteria or were of sufficient interest on other grounds. Each of these studies was assigned to two committee members for coding on 16 study characteristics that the committee judged to be potentially relevant to an assessment of the polygraph’s accuracy. (Appendix G provides details on the committee’s process.)

We conducted a systematic review of research but not a meta-analysis for two basic reasons.1 First, the studies of adequate quality are too het-



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement