Polygraph testing abuses in National Registry of Exonerations false confession cases

Abstract

Purpose

We investigated the context and consequences of polygraph administration during the interrogation of criminal suspects who falsely confessed and were later exonerated. We expected that polygraph results for these exonerees would reflect false positives, or cases in which innocent suspects were told they failed when they actually passed.

Method

Based on false confession cases documented by the National Registry of Exonerations, we reviewed original source documents to identify instances where a polygraph was administered during interrogation, resulting in a final sample of 56 cases. Case documents were reviewed to determine the polygraph outcome, how the outcome was conveyed to the exoneree, the strength of evidence implicating the exonerees prior to polygraph administration, and the presence of demographic and psychological vulnerabilities previously associated with false confessions.

Results

Of the 36 cases where polygraph examiner decisions were reported, only eight were accurate. In all but one case, suspects were told that the polygraph indicated deception, even when inconclusive or exculpatory. Polygraphs were often administered in the absence of strong incriminating evidence and to individuals who possessed vulnerabilities known to increase false confession risk.

Conclusions

These results represent the largest known repository of cases involving polygraphic interrogation of demonstrably innocent individuals who falsely confessed. None of the exonerees benefited from taking the polygraph, regardless of the outcome. We refer to the use of polygraphs to convince suspects they have been incriminated by their own bodily responses as a Polygraph Self-Incrimination Ploy, an interrogation technique that contributes to false confessions in vulnerable individuals.