To act truthfully: Nonverbal behaviour and strategies during a police interrogation

Abstract

In an experiment, nonverbal indicators of deception in police interrogations of mock crimes were examined. Both vocal and nonvocal behaviours were scored. Thirty participants were subjected to long interrogations (over 9 minutes) conducted by 30 experienced police officers, asked to interrogate as they normally do. Although the liars reported being significantly more nervous, and found the task more strenuous than the truth tellers, no differences in the nonverbal behaviours scored were found. In an analysis of the strategies employed, both truth tellers and liars were found to try to not make excess movements. The principal verbal content strategy for the liars was to keep the story simple, and for truth tellers to keep the story real. The reasons why, in this demanding situation, the truth tellers and liars could not be distinguished by their nonverbal behaviour are discussed.

Keywords:

• Nonverbal behaviour
• cues to deception
• police interrogations
• truth teller's and liar's strategies

This research was sponsored by a grant from The Swedish Research Council to the third author. We thank Malin Olsson and Fredrik Good for help with the coding of the videotapes. We also thank Karl Ask, Lina Bengtsson, Niklas Fransson, Anneli Larsson, Lina Leander, Viktor Prytz, and Johan Tengström for help with the data collection, Detective Superintendent Royne Nilsson for granting us the opportunity to conduct this research, and an anonymous reviewer for helpful suggestions.

Notes

1. Here we present a short description of some key features of the interrogations: All but two interrogators asked the suspect for a free recall. This occurred mostly during the first part of the interrogations. On average, the interrogators posed more closed than open-ended questions. The interrogations typically contained a number of interruptions from the interrogator, and the interrogator frequently posed several repeated questions. On average, only slightly more words were spoken by the suspect than by the interrogator. For the full results of the interrogation analyses, see Hartwig et al. (in press).

2. Because of poor sound quality in six of the videotaped interrogations, the vocal behaviours (the two pauses measures, ahs speech disturbances and speech rate) could not accurately be scored for them.