Lineup Composition Effects on Eyewitness Identification

Abstract

Whenever lineups are prepared for eyewitness identification, the investigator constructing the lineup must decide how to choose lineup members to appear in the lineup with the person under investigation. Accordingly, three research projects were conducted to inform lineup construction practices. The first project is a meta-analysis of lineup similarity effects. Results of the meta-analysis suggest that biased lineups yield the highest rate of suspect identifications, regardless of whether that person is guilty or innocent. When lineups with moderately similar members are compared with lineups containing highly similar members, increasing similarity reduces innocent suspect identifications and has only a small and nonsignificant effect on correct identifications. Two experimental studies were then conducted using morphing software to systematically manipulate the degree of similarity between lineup members who are known be innocent (fillers) and the lineup member who is under investigation (the suspect). In the first experiment, lineups with moderately high similarity fillers yielded a higher correct identification rate than did lineups with very high similarity fillers. When comparable procedures were used in the second experiment, fillers of low and moderately low similarity to the culprit yielded nearly identical correct identification rates. In both experiments, increasing suspect-filler similarity led to a decrease in innocent suspect misidentifications. The accumulation of evidence from the three research projects suggests lineups would be best constructed with fillers of moderate similarity to the suspect.