Evidence strength (insufficiently) affects police officers' decisions to place a suspect in a lineup

We examined whether variations in the strength of the evidentiary connection between a suspect and the crime under investigation affected officers' decisions to place suspects into an identification procedure and whether education about the problems associated with base-rate neglect sensitized officers to variations in evidentiary connection.

Police officers (N = 279; age range = 24-70; 86% male) read a hypothetical crime scenario, adopting the role of the lead investigator. The scenarios varied in how closely the suspect was connected to the crime (evidentiary connection: weak vs. strong). Before reading the crime scenarios, half of the participants received education about the relationship between the base rate of guilt among suspects placed in lineups and the prevalence of mistaken identifications (education: present vs. absent). Officers indicated whether they would conduct an identification procedure with a witness based on the evidence they currently had against the suspect.

We expected that participants would better distinguish between the strong and weak evidentiary connection conditions when education was present than when it was absent.

Education did not sensitize officers to the strength of the evidence connecting the suspect to the crime under investigation, but officers were sensitive to variations in evidentiary connection without benefit of the educational intervention. However, a majority of officers were willing to subject a suspect to an identification procedure even when there was no evidence connecting the suspect to the crime.

Officers' decisions about placing suspects in lineups reflect some level of base-rate neglect that remained even after education about the importance of increasing the ratio of culprit-present to culprit-absent lineups for decreasing mistaken identifications. (PsycInfo Database Record (c) 2022 APA, all rights reserved).