Response biases in lineups and showups.

The showup, or presentation of a single suspect to an eyewitness, is widely believed to be a more biased and suggestive identification procedure than the lineup even though there has been no empirical work on this issue. Results suggest, however, that witnesses at a lineup are less likely to say «not there» than are witnesses at a showup. This tendency is seen in both live and photographic identification procedures, in both laboratory studies and real-world identifications. Showups in the lab resulted in no more mistaken identifications than lineups. Results also suggest that a showup is not equivalent to a poor lineup (i.e., a lineup with a functional size of 1)