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

Abstract

Objective: 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. Method: 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. Hypotheses: We expected that participants would better distinguish between the strong and weak evidentiary connection conditions when education was present than when it was absent. Results: 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. Conclusions: 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. Public Significance StatementEyewitness misidentifications are the leading cause of wrongful convictions. Police officers reported that they would be less likely to place a suspect in a lineup when the evidence connecting the suspect to the crime was weak, yet a majority of officers were willing to subject a suspect to identification procedures even when there was no evidence connecting the suspect to the crime under investigation. This willingness to conduct identification procedures in the absence of evidence connecting the suspect to the crime puts innocent suspects at risk of misidentification.

Potential causes of racial disparities in wrongful convictions based on mistaken identifications: Own-race bias and differences in evidence-based suspicion.

“…Although the proportion of officers who were willing to place the suspect into a lineup was greater when the evidentiary connection was strong than when it was weak, the majority of participants (74%) who read a scenario in which there was essentially no evidence connecting the suspect to the crime indicated that they would ask a witness to attempt an identification of the suspect. Even if the witness made a positive identification of the suspect, the posterior probability of the suspect’s guilt would be only 64% because the prior probability of guilt was so low (Katzman & Kovera, 2022).…”

“…The latest scholarly recommendations for evidence-based procedures that police should follow when collecting eyewitness identification evidence include having evidence-based suspicion—that is, evidence linking a specific suspect to a specific crime—before placing a suspect in an identification procedure (Wells et al, 2020). Requiring police to have evidence-based suspicion before conducting identification procedures increases the base rate of guilty suspects in those procedures, which in turn increases the likelihood that positive identifications of suspects are correct identifications (Katzman & Kovera, 2022; Wells et al, 2015). As we will explain in the following section, even if witness performance remains the same (i.e., there are no changes in the rates at which witnesses make correct and mistaken identifications of suspects), the ratio of correct to incorrect identifications increases as the base rate of target-present identification procedures increases.…”

Evidence-based suspicion and the prior probability of guilt in police interrogations.

“…Additional work on police decision-making will help establish boundaries for implementing this standard, too. Recent work has suggested that police are sensitive to variations in evidence strength but often choose to put suspects in a lineup even when the base rate is low (Katzman & Kovera, 2022). Moreover, police might evaluate evidence strength more objectively when it is presented in alternative formats, such as likelihood ratios (Cabell et al, 2022).…”

The role of suspect development practices in eyewitness identification accuracy and racial disparities in wrongful conviction

“…Research on whether actors in the criminal legal system recognize the importance of the base‐rate of guilty culprits in identification procedures is quite limited. In the first experimental examination of this question (Katzman & Kovera, 2022), police officers read a description of a robbery and information about how police identified a potential suspect for that robbery (e.g., found in the vicinity of the crime, recently arrested for a crime with a similar modus operandi). We varied the strength of the evidence connecting the suspect with the specific crime the officer was investigating.…”

“…The authors of the recommendations specifically made a distinction between reasonable suspicion and evidence‐based suspicion given that case law allows for reasonable suspicion to be nothing more than a police officer's hunch. With more guilty suspects in lineups, an identification of a suspect results in a higher posterior probability of guilt and fewer misidentifications (Katzman & Kovera, 2022; Wells et al., 2015).…”