Designing police lineups to maximize memory performance

How can lineups be designed to elicit the best achievable memory performance? One step toward that goal is to compare lineup procedures. In a recent comparison of US and UK lineup procedures, discriminability and reliability was better when memory was tested using the US procedure. However, because there are so many differences between the procedures, it is unclear what explains this superior performance. The main goal of the current research is therefore to systematically isolate the differences between the US and UK lineups to determine their effects on discriminability and reliability. In five experiments, we compared (1) presentation format: simultaneous vs. sequential; (2) stimulus format: photos vs. videos; (3) number of views: 1-lap vs. 2-lap vs. choice in both video and photo lineups; and (4) lineup size: 6- versus 9-lineup members. Most of the comparisons did not show appreciable differences, but one comparison did: simultaneous presentation yielded better discriminability than sequential presentation. If the results replicate, then policymakers should recommend using a simultaneous lineup procedure. Moreover, consistent with previous research, identifications made with high confidence were higher in reliability than identifications made with low confidence. Thus, official lineup protocols should require collecting confidence because of the diagnostic value added.