Detection of culprit presence in multiple-culprit crimes: A comparison of combined and separate lineup-presentation formats

Abstract

Although crimes involving multiple culprits are widespread, there is still a lack of understanding of how the police should construct lineups for multiple suspects in these cases. In most of the few guidelines that exist it is recommended to present multiple lineups separately in succession, with each lineup including one suspect. This replicates, for each suspect in a multiple-culprit case, the procedure used for a single suspect in a single-culprit case. However, this recommendation could be reconsidered if it turned out that, if multiple culprits are present in the lineups, the face of one culprit serves as a contextual facial cue that enhances the eyewitness’s ability to detect another culprit within the same display—an effect that could only occur if all lineups are presented together in a combined lineup-presentation format, allowing them to be visible concurrently. Two experiments using a staged-crime video with four culprits were conducted to test whether presenting simultaneous lineups combined as opposed to separately affects culprit-presence detection. In Experiment 1, it was tested whether culprit-presence detection differs between combined and separate lineup-presentation formats. No significant difference was found, indicating comparable performance between the two lineup-presentation formats. In Experiment 2, we compared a condition in which three culprit-present lineups were combined—allowing for multiple potential contextual facial cues—with conditions involving separate lineups and combined lineups with only one culprit-present lineup, where contextual facial cueing was theoretically not possible. Culprit-presence detection did not differ between the combined format with three culprit-present lineups and the other conditions. Given the absence of clear benefits of the combined-lineup-presentation format, a cautious, pragmatic conclusion is to continue presenting each suspect in a separate lineup, consistent with most current recommendations.