The Distance Threshold (PRE-PRINT)

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 and rejection accuracy, confidence, and 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 four live targets at distances between 5-110 meters (m) using an eight-person computerized line-up task. We employed simultaneous and sequential target-absent or target-present line-ups and presented these to 1588 participants (age range 6-77; 61% female, 95% Finns) resulting in 6233 responses. We found that at 40m diagnosticity was 50% lower than at 5m, and with increased distance diagnosticity tapered off until it was 1 (+/- 0.5) at 100m for all age groups and line-up types. However, young children (6-11) and older adults (45-77) reached a diagnosticity of 1 at shorter distances compared with older children (12-17) and young adults (18-44). We found that with increased distance, confidence dropped whereas response time remained stable, and that high confidence and shorter response times were associated with identification accuracy up to 40m. 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.