The distance threshold of reliable eyewitness identification

Abstract

Increased distance between an eyewitness and a culprit decreases the accuracy of eyewitness identifications, but the maximum distance at which reliable observations can still be made is unknown. Our aim was to identify this threshold. We hypothesized that increased distance would decrease identification, rejection accuracy, confidence and would increase response time. We expected an interaction effect, where increased distance would more negatively affect younger and older participants (vs. young adults), resulting in age-group specific distance thresholds where diagnosticity would be 1. We presented participants with 4 live targets at distances between 5 m and 110 m using an 8-person computerized line-up task. We used simultaneous and sequential target-absent or target-present line-ups and presented these to 1,588 participants (age range = 6-77; 61% female; 95% Finns), resulting in 6,233 responses. We found that at 40 m diagnosticity was 50% lower than at 5 m and with increased distance diagnosticity tapered off until it was 1 (±0.5) at 100 m for all age groups and line-up types. However, young children (age range = 6-11) and older adults (age range = 45-77) reached a diagnosticity of 1 at shorter distances compared with older children (age range = 12-17) and young adults (age range = 18-44). We found that confidence dropped with increased distance, response time remained stable, and high confidence and shorter response times were associated with identification accuracy up to 40 m. We conclude that age and line-up type moderate the effect distance has on eyewitness accuracy and that there are perceptual distance thresholds at which an eyewitness can no longer reliably encode and later identify a culprit.