Eyewitness metamemory predicts identification performance in biased and unbiased line-ups

Purpose: Distinguishing accurate from inaccurate identifications is a challenging issue in the criminal justice system, especially for biased police line-ups. That is because biased line-ups undermine the diagnostic value of accuracy postdictors such as confidence and decision time. Here, we aimed to test general and eyewitness-specific self-ratings of memory capacity as potential estimators of identification performance that are unaffected by line-up bias. Methods: Participants (N = 744) completed a metamemory assessment consisting of the Multifactorial Metamemory Questionnaire and the Eyewitness Metamemory Scale and took part in a standard eyewitness paradigm. Following the presentation of a mock-crime video, they viewed either biased or unbiased line-ups. Results: Self-ratings of discontentment with eyewitness memory ability were indicative of identification accuracy for both biased and unbiased line-ups. Participants who scored low on eyewitness metamemory factors also displayed a stronger confidence–accuracy calibration than those who scored high. Conclusions: These results suggest a promising role for self-ratings of memory capacity in the evaluation of eyewitness identifications, while also advancing theory on self-assessments for different memory systems.