Double-blind photoarray administration as a safeguard against investigator bias.

This experiment examined whether a photoarray administrator's knowledge of a suspect's identity increased false identification rates. Fifty participant-administrators (PAs) presented 50 participant-witnesses (PWs) two perpetrator-absent photoarrays following a live staged crime involving two perpetrators. For one photoarray per trial, the experimenter revealed the suspect's identity to the PA. Each PA presented the photoarrays sequentially or simultaneously in the presence or absence of an observer. When the observer was present, PA knowledge of the suspect's identity had a biasing effect in sequential photoarrays only. This pattern did not emerge when the observer was absent. The experimental manipulations did not affect PAs' and PWs' ratings of photoarray fairness or PWs' ratings of pressure to make an identification. These data suggest that only administrators who are blind to the suspect's identity should present sequential photoarrays.