Identification accuracy for single- and double-perpetrator crimes: does accomplice gender matter?

There is an important mismatch between empirical research on the accuracy of eyewitness identification and the real world of criminal investigation. Most research models single-perpetrator crimes, but in the real world, most crimes involve multiple perpetrators. This study examined how the number of perpetrators affects eyewitness identification by manipulating the gender of accomplices. Observers viewed a video of a staged crime. The crime was committed by a male or female perpetrator, who was presented alone or with an accomplice of the same or the opposite gender. The observers were then asked to identify the perpetrators from target-present or target-absent line-ups. The results revealed a double-perpetrator disadvantage, which was manifested in reduced identification accuracy on target-present line-ups. Importantly, however, the gender of the perpetrator or the accomplice had no effect on this disadvantage. This double-perpetrator disadvantage is attributed to the need to divide attention between two concurrent people, compared to single-culprit crimes, rather than an impairment of visual encoding processes. The implications of these findings are discussed.