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Is the Inference Rule of the "Control Question Polygraph Technique" Plausible?

NCJ Number
206691
Journal
Psychology Crime & Law Volume: 9 Issue: 1 Dated: 2003 Pages: 37-47
Author(s)
Eitan Elaad
Date Published
2003
Length
11 pages
Annotation
This article reports on two experiments that were designed to determine whether the inference rule suggested for the controversial control question technique (CQT) in polygraph examinations is valid.
Abstract
In the CQT, three types of questions are asked of the examinee. "Relevant" questions pertain directly to the crime under investigation; "control" questions address matters related to what the examinee has done in the past; and "irrelevant" questions are administered to absorb the initial orienting response evoked by an opening question and to enable rest periods between the more emotional questions. The assumption underlying the CQT is that each examinee will focus his/her concern on the questions that present the greatest threat of failing the test; hence, the inference rule on which the CQT is based predicts that guilty examinees will show greater concern about the specific relevant questions than about the more general "control" questions. Innocent examinees, on the other hand, will manifest the opposite pattern in having more concern about the control questions to which they are lying than about the relevant questions to which they are responding with the truth. The major argument against the CQT inference rule is that it is not logical, because for a suspect in a real-life crime, the polygraph test is but one part of the broader investigative process in which the relevant questions play a major role; therefore, the relevant questions that focus on the investigated crime should not be expected to yield the concern equivalent to the more general control questions; this should be true for both innocent and guilty suspects. In one of the experiments reported in this article, a story of a hypothetical theft was presented to 20 police interrogators. Half of the participants were presented with a story about a guilty suspect, and the other half were given a similar story that described an innocent suspect. The interrogators were asked to assess the concern that this person would experience when various questions were presented to him in a polygraph test. Results supported the reasoning of the inference rule proposed for the CQT. The second experiment extended the plausibility question about the CQT to predictions about the relative frequencies of truthful and deceptive outcomes. Opponents of the CQT argued that many innocent examinees would show larger physiological responses to relevant questions than to control questions, thus yielding deceptive outcomes. Analysis of a random sample of actual polygraph tests showed that truthful outcomes were more common than predicted. Based on these two experiments, this article concludes that the CQT is not more or less valid than indicated by the critical view of the CQT, but the less frequent false negative outcomes (indicating that a guilty examinee is truthful) replace the more frequent false positive errors. The author recommends that this claim be examined in a separate study. 5 tables and 11 references