Effect of retention interval on showup and lineup performance

Showups – when a single suspect is presented to an eyewitness – are thought to be a more suggestive procedure than traditional lineups by the U.S. Supreme Court and social science researchers. The present experiment examined the impact of retention interval on showup identifications, because immediate showups might be no worse than, and perhaps even better than, a lineup conducted after a delay. Participants (N = 1584) viewed a mock-crime video and then were presented with a showup or a simultaneous lineup, either immediately or a 48 h delay. Receiver operating characteristic (ROC) analyses revealed that a showup never resulted in better identification accuracy than a lineup. We conclude with a discussion of whether showups should ever be used.