An evaluation of lineup presentation, weapon presence, and a distinctive feature using ROC analysis

•We applied ROC analysis to system and estimator variables to assess discriminability between innocent and guilty suspects.•The simultaneous lineup produced higher discriminability than the sequential lineup.•The presence of a weapon during the mock crime reduced discriminability during the lineup.•A salient feature on the perpetrator and all lineup members reduced discriminability more so than the weapon.•The weapon effect was eliminated when the perpetrator and all lineup members had the distinctive facial feature.

We conducted an experiment (N = 2675) including both laboratory and online participants to test hypotheses regarding important system and estimator variables for eyewitness identification. Simultaneous lineups were compared to sequential lineups with the suspect presented early versus late because there is evidence that suspect position could be an important factor determining a simultaneous versus sequential advantage in guilty-innocent suspect discriminability. We also manipulated whether or not the perpetrator held a weapon or had a distinctive feature on his face, to re-evaluate recent evidence that these factors interact. Overall, the simultaneous lineup yielded higher discriminability than the sequential lineup, and there was no effect of sequential position. Discriminability was higher when the perpetrator had no weapon, but only when no distinctive feature was present. We conclude with a discussion of the importance of exploring interactions between system and estimator variables using Receiver Operating Characteristic (ROC) analysis.