The number of fillers may not matter as long as they all match the description: The effect of simultaneous lineup size on eyewitness identification

Abstract

SummaryAccording to the Diagnostic Feature‐Detection (DFD) hypothesis, the presence of fillers that match the eyewitness's description of the perpetrator will boost discriminability beyond a showup, and very few fillers may suffice to produce the advantage. We tested this hypothesis by comparing showups with simultaneous lineups of size 3, 6, 9, and 12. Participants (N = 10,433) were randomly assigned to one of these conditions, as well as target‐present (TP) versus target‐absent (TA) lineup. As predicted by the DFD hypothesis, lineups were superior to showups, and there was no advantage with increased lineup size beyond a 3‐member lineup. The confidence‐accuracy (CA) relationship held a similar pattern. The only effect of increased lineup size was a lower likelihood of choosing a suspect (guilty or innocent). We conclude that police should focus more on the quality rather than quantity of fillers.