Refining the blank lineup procedure: how should we instruct eyewitnesses?

Presenting a blank lineup—containing only fillers—to witnesses prior to showing a real lineup might be useful for screening out those who pick from the blank lineup as unreliable witnesses. We show that the effectiveness of this procedure varies depending on instructions given to witnesses. Participants (N = 462) viewed a simulated crime and attempted to identify the perpetrator from a lineup approximately one week later. Rejecting a blank lineup was associated with greater identification accuracy and greater diagnosticity of suspect identifications, but only when witnesses were instructed prior to the blank lineup that they would view a series of lineups; the procedure was ineffective for screening when witnesses were advised they would view two lineups or received no instruction. These results highlight the importance of instructions used in the blank lineup procedure, and the need for better understanding of how to interpret choosing patterns in this paradigm.