Effective Policing

Abstract

Forensic applications of polygraph techniques rely primarily on the control or comparison question test (CQT). The author describes the CQT and its theoretical basis, and how it is used and evaluated by the polygraph professionals, and by scientists at arms length from the polygraph community. Because the CQT (a) has a weak theoretical foundation, making it unlikely that it can be as accurate as polygraph proponents claim, (b) is biased against the innocent, and (c) may be subject to countermeasures used by the guilty to appear truthful, CQT results cannot constitute evidence of either deception or truthfulness. In the absence of insight into brain mechanisms that underlie deception, it may be difficult to develop a valid lie detector. However, methods are available for detecting guilty knowledge, information that only the perpetrator of a crime and the police possess, which are ripe for further development as forensic applications.

A review of the polygraph: history, methodology and current status

“…It is important to note that, while all three stages of the CQT examination can be criticized on the grounds of lacking objectivity and standardization, it is the CQT's theoretical underpinning and its derived assumptions that have drawn the most criticisms; especially the notion that an innocent examinee will respond more strongly to a comparison question than to a relevant question (Fiedler, Schmid, & Stahl, 2002;Iacono, 2008;Lykken, 1998). The basic idea behind this notion is that an innocent examinee would (a) believe that the polygraph will detect their honesty in response to the relevant questions, and (b) would subsequently be more worried about their lies in response to the comparison questions being detected, resulting in different physiological patterns of arousal between truth-tellers and liars (Horvath & Palmatier, 2008).…”

“…Field studies supporting the effectiveness of the CQT (e.g. Mangan, Armitage, & Adams, 2008) are often criticized on the basis that their criterion for establishing ground truth is confession, which inflates accuracy estimates by creating a sampling bias (Iacono, 2008;Patrick & Iacono, 1991). Accuracy estimates of the CQT range from 74% to 89% for guilty examinees, with 1% to 13% false-negatives, and 59% to 83% for innocent examinees, with a false-positive ratio varying from 10% to 23% (Grubin, 2010).…”

“…Rather than competing for dominance, the polygraph-and P300-based CIT are complimentary techniques, and there is little conflict between the academic communities respectively researching them (Iacono, 2008).…”

Deceptive intent

“…In addition to self-reported cognitive load and stress, we also assessed the interviewee's sympathetic nervous system (SNS) activity in the form of EDA. Increased SNS and EDA activity is typically associated with deception/lying (e.g., Vincent & Furedy, 1992;Watson & Sinha, 1993) and even forms the basis of the polygraph (Iacono, 2008;Vrij, 2008). However, theoretically it is not clear yet which psychological processes lead to increased EDA during deception.…”

The effects of examiner personality variables and training on the accuracy of detection of deception

“…The post-test phase is thus a complex phase and varies in accordance to the examiners' personal style. Examiners may adopt a variety of interviewing strategies, reasoning or persuasion techniques to gain better insight on the issue under investigation or to elicit a confession (Iacono, 2008).…”