Eyewitness Identification: A Systematic Investigation of Lineup Composition and Fairness, United States, 2019-2022

The major objective of this project was to investigate photo array composition in order to improve eyewitness identification procedures. Photo array composition involves the fillers, or known-innocent individuals that police add to a photo array so that the perpetrator/suspect (referred to as the "target" in experimental design) does not stand out. An unbiased (fair) photo array contains fillers that match the description of the suspect provided by one or more eyewitnesses. In contrast, in a biased photo array, the suspect stands out from the fillers. Another popular procedure used by police is the showup, when the suspect is presented without any fillers. This project involved all three of these procedures.

This collection contains raw and aggregated data from 12 sets of experiments that investigated different aspects of eyewitness identification, including fair vs. biased lineups, lineup size, distinctive facial features, target-filler similarity, impact of sleep on eyewitness accuracy, memory strength, number of suspects presented, impact of courtroom instructions and expert expertise, and speed and confidence of eyewitness identification. Each experiment set followed a similar general design, with variations based on the purpose and hypotheses of the specific study. United States-based adult participants recruited via SurveyMonkey were asked to complete an online experiment in which they would be presented with a crime vignette and a suspect facial image (created from a faces database), given a distractor task, and then asked to select the suspect from a lineup and rate the confidence level of their decision.

The data were provided to ICPSR in Excel workbook format (41 data files, 3 codebooks) and are available for download as a zipped package. ICPSR has not modified the files from the format in which they were supplied. Data files are organized into subfolders that are named with a short content descriptor and citation of the relevant publication. Unless noted, data files contain a "codes" sheet that explains the variables and experimental condition groups. Articles and theses/dissertations that used each dataset are available under Data-related Publications. Please refer to the ICPSR README for more information.