Deception among pairs: “Let's say we had lunch and hope they will swallow it!”

Abstract

Deception research has neglected the fact that legal-workers often have to try to detect deceit on the basis of statements derived from pairs of suspects, each having been interrogated repeatedly. To remedy this shortcoming we conducted a study where each member of 10 truth-telling pairs and 10 lying pairs was interrogated twice about an alibi. One hundred and twenty undergraduate students were enrolled as lie-catchers. The main findings were that (a) overall deception detection accuracy was modest; (b) lie-catchers given access to a large number of statements did not outperform lie-catchers given access to a lesser number of statements; (c) when asked to justify their veracity assessments the most frequently reported cue was ‘consistency within pairs of suspects’; (d) all cues to deception were of low diagnostic value. Psycho-legal aspects of integrating sequential information in deception detection contexts are discussed.

Keywords:

• Deception detection
• Repeated interrogations
• Pairs of suspects
• Diagnostic values of cues to deception

This study was supported by a grant (F0505-97) from the Swedish Council for Research in the Humanities and Social Sciences given to the second author. Parts of this research were presented at the 10^th European Conference of Psychology and Law, Limassol, Cyprus, April 2000. We thank Mathias Garhed and Jonas Thörnqvist for their help with collecting the data.

Notes

¹For example, a diagnostic value of 4.0 for a particular of cue tells us that it is four times more likely that a veracity judgment based on this cue will be correct than incorrect. Put differently, a DV of 4 means that 80 out of every 100 veracity judgments based solely on this cue would turn out to be correct. According to Wagenaar, van Koppen and Crombag (1993) the diagnostic values found in forensic contexts typically vary between 1.0 and 2.0, and rarely exceed 5.0.

²This criteria excluded two categories of cues: ‘Confidence’ and ‘Facial expressions’.