tion admissions or confessions occurred and on whether the admitted acts corresponded to significant responses to relevant questions about those specific acts, information from current field screening examinations would have limited value for assessing validity because of the need for independent validation of the admissions and confessions.
There is in fact no direct scientific evidence assessing the value of the polygraph as a deterrent, as a way to elicit admissions and confessions, or as a means of supporting public confidence. What indirect scientific evidence exists does support the plausibility of these uses, however. This evidence implies that for the polygraph or any other physiological technique to achieve maximal utility, examinees and the public must perceive that there is a high likelihood of deception being detected and that the costs of being judged deceptive are substantial. If people do not have these beliefs, then the value of the technique as a deterrent, as an aid to interrogation, and for building public confidence, is greatly diminished. Indeed, if the public does not believe a technique such as the polygraph is valid, using it to help reinstate public trust after a highly visible security breach may be counterproductive.
Regardless of people’s current beliefs about validity, if polygraph testing is not in fact highly accurate in distinguishing truthful from deceptive responses, the argument for utility diminishes in force. Convincing arguments could then be made that (a) polygraphs provide a false sense of security, (b) the time and resources spent on the polygraph would be better spent developing alternative procedures, (c) competent or highly skilled individuals would be or are being lost due to suspicions cast on them by erroneous decisions based on polygraph tests, (d) agencies that use polygraphs are infringing civil liberties for insufficient benefits to the national security, and (e) utility will decrease rapidly over time as people come to appreciate the low validity of polygraph testing. Polygraph opponents already make such arguments.
The utility benefits claimed for the polygraph, even though many of them are logically independent of its validity, depend indirectly on the polygraph being a highly valid indicator of deception. In the long run, evidence that supports validity can only increase the polygraph test’s utility and evidence against validity can only decrease utility. The scientific evidence for the ability of the polygraph test to detect deception is therefore crucial to the test’s usefulness. The evidence on validity is discussed in Chapters 3, 4, and 5.
For the polygraph test to be considered a valid indicator of deception, it must perform better against an appropriate criterion of truth than do