Double-blind photoarray administration as a safeguard against investigatorbias

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