Andrew J. Evelo

Cops and robbers (and eyewitnesses): a comparison of lineup administration by robbery detectives in the USA and Canada

The purpose of this study was to determine how American and Canadian robbery detectives collect identification evidence and whether their practices are consistent with published guidelines. Via a survey, we asked about the use of various lineup practices (e.g., single-blind vs. double-blind administration, sequential vs. simultaneous presentation, and videotaping). Canadian detectives are more likely to use research-based reforms such as double-blind sequential lineups and videotaping. We also assessed how robbery detectives interact with eyewitnesses at four points during a lineup: prior to the lineup, immediately after an identification, and after 12 seconds and 3 minutes have elapsed without an identification. Results showed that at the latter two junctures, officers from both the countries question eyewitnesses in subtle ways that could influence the likelihood of choosing and confidence in the selection. Canadian detectives are less likely than American detectives to do so, however. This finding can be explained by the absence of written guidelines in most US jurisdictions on how officials should interact with eyewitnesses during lineups.

The case for double-blind lineup administration.

Many have recommended that lineups be conducted by administrators who do not know which lineup member is the suspect (i.e., a double-blind administration). Single-blind lineup administration, in which the administrator knows which lineup member is the suspect, increases the rate at which witnesses identify suspects, increasing the likelihood that both innocent and guilty suspects are identified. Although the increase in correct identifications of the guilty may appear desirable, in fact, this increase in correct identifications is the result of impermissible suggestion on the part of the administrator. In addition to these effects on witness choices, single-blind administration influences witness confidence through an administrator’s feedback to witnesses about their choices, reducing the correlation between witness confidence and accuracy. Finally, single-blind administration influences police reports of the witness’s identification behavior, with the same witness behavior resulting in different outcomes for suspects depending upon whether the administrator knew which lineup member was the suspect. Administrators who know which lineup member is the suspect in an identification procedure emit behaviors that increase the likelihood that witnesses will choose the suspect, primarily by causing witnesses who would have chosen a filler (known innocent member of the lineup who is not the suspect) to choose the suspect. To avoid impermissible suggestion, photo arrays and lineups should be administered using double-blind procedures.

Memory strength and lineup presentation moderate effects of administrator influence on mistaken identifications.

Administrator/witness pairs (N = 313) were randomly assigned to target-absent lineups in a 2 (Suspect/Perpetrator Similarity: High Suspect Similarity vs. Low Suspect Similarity) × 2 (Retention Interval: 30 min vs. 1 week) × 2 (Lineup Presentation: Simultaneous vs. Sequential) × 2 (Administrator Knowledge: Single-Blind vs. Double-Blind) factorial design to test whether suspect similarity and memory strength constrain interpersonal expectancy effects on eyewitness identification accuracy. Administrators who knew which lineup member was the suspect (single-blind) or who administered simultaneous lineups were more likely to emit verbal and nonverbal behaviors that suggested to the witness who the suspect was. Additionally, single-blind administrators exerted more pressure on witnesses to choose the suspect as opposed to fillers. Administrator knowledge interacted with retention interval and lineup presentation to influence mistaken identifications of innocent suspects; witnesses were more likely to mistakenly identify an innocent suspect from single-blind than double-blind lineups when witness retention intervals were long and photographs were presented simultaneously. Contrary to our predictions, suspect/perpetrator similarity did not interact with other manipulated variables to influence identification decisions. Both sequential and double-blind procedures should be used to reduce the use of suggestive behavior during lineup administration.