a b s t r a c tShowups -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.

Showups (a one-person identification) were compared to both simultaneous and sequential lineups that varied in lineup fairness and the position of the suspect in the lineup. We reanalyzed data from a study by Gronlund, Carlson, Dailey, and Goodsell (2009), which included simultaneous and sequential lineups, and using the same stimuli and procedures, collected new data using showup identifications. Performance was compared using ROC analysis, which is superior to traditional measures such as correct and false identification rates, and probative value measures. ROC analysis showed that simultaneous lineups consistently produced more accurate identification evidence than showups, but sequential lineups were sometimes no more accurate than showups, and were never more accurate than simultaneous lineups. These results supported prior suppositions regarding the suggestiveness of showups, revealed a misconception about the superiority of sequential lineups, and demonstrated why eyewitness identification procedures need to be evaluated using ROC analyses.

We thank 1) the London Metropolitan Police Officers who assisted with the materials used in these experiments; 2) Stanislav Wronski for programming many of the experiments; 3) John T. Wixted and Shiri Lev-Ari for discussions about this research; and 4) Harold Pashler for recommending that our figures reflect the number of responses per point.

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