Lineups

Lineups are conducted in the course of police investigations when a crime has been witnessed by one or more people. A lineup typically consists of a person whom the police believe committed the crime (i.e., the suspect) and some number of people who are known to be innocent of the crime (i.e., fillers). When the police have developed a suspect, they show witnesses a lineup to test whether they will claim that the suspect is the person who committed the crime (i.e., the perpetrator). If so, the witness is said to have made a positive identification of the suspect. What is not clear, at least in real-world investigations, is whether that identification is correct, because sometimes suspects are guilty and sometimes they are innocent. Since the late 1970s, psychologists have conducted experiments to find lineup procedures that decrease the likelihood that witnesses will mistakenly identify innocent suspects. These experiments are typically conducted in laboratory settings in which researchers expose participants to a simulated crime, often on videotape. After the participant-witnesses have viewed the crime, they are asked to attempt an identification from a lineup. In the laboratory, researchers can vary whether the perpetrator appears in that lineup. When the perpetrator is present in the lineup (i.e., a target-present lineup), the witness can identify the suspect (a correct identification), identify a filler, or say that the perpetrator is not there (an incorrect rejection of the lineup). When the perpetrator is not present (i.e., a target-absent lineup), the witness can make a mistaken identification of the suspect, identify a filler, or correctly reject the lineup. Using this method, researchers have identified lineup procedures that decrease mistaken identifications, which are the leading cause of wrongful convictions among those who have been exonerated by DNA tests conducted after trial. This article contains sections describing comprehensive General Overviews of research on lineups, research demonstrating that Live Lineups Are Equivalent to Photo Lineups, and Policy Recommendations and Best Practice Guidelines. The remaining sections describe many of these policy recommendations, including how Lineups Are Superior to Showups, having an Evidence-Based Suspicion for placing a suspect in a lineup, unbiased Lineup Composition, Double-Blind Administration, proper Lineup Instructions, collecting witnesses’ Confidence Statements in the accuracy of their identification immediately after the initial identification, Video Recording Identification Procedures, and avoiding Repeated Lineups. An additional section addresses special issues that need to be considered when Conducting Lineups with Children.

Do Sequential Lineups Impair Discriminability?

The debate regarding the best way to test and measure eyewitness memory has dominated the eyewitness literature for more than thirty years. We argue that to resolve this debate requires the development and application of appropriate measurement models. In this study we develop models of simultaneous and sequential lineup presentations and use these to compare the procedures in terms of discriminability and response bias. We tested a key prediction of the diagnostic feature detection hypothesis that discriminability should be greater for simultaneous than sequential lineups. We fit the models to the corpus of studies originally described by Palmer and Brewer (2012, Law and Human Behavior, 36(3), 247-255) and to data from a new experiment. The results of both investigations showed that discriminability did not differ between the two procedures, while responses were more conservative for sequential presentation compared to simultaneous presentation. We conclude that the two procedures do not differ in the efficiency with which they allow eyewitness memory to be expressed. We discuss the implications of this for the diagnostic feature detection hypothesis and other sequential lineup procedures used in current jurisdictions.

Factors That Can Interact with Familiarity

This chapter discusses system variables that are under the control of the criminal justice system and can be manipulated after the crime has occurred, such as the type of lineup procedure shown to the eyewitness. The chapter first discusses recall memory and the different interviewing protocols and how these may interact with familiarity to influence an eyewitness’ memory of the perpetrator as well as the environment and event. Next, the chapter focuses on recognition memory, specifically lineup identification. The different lineup procedures used to collect eyewitness evidence are discussed, in addition to how each procedure may promote higher rates of accuracy and eyewitness confidence when a familiar-stranger is the perpetrator. Last, the chapter discusses unconscious transference and the commitment effect.

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.

Metacognitive Control and Lineup Instructions: Asking eyewitnesses to recollect reduces false identification

Little theoretically-informed research investigates how non-traditional lineup tasks or metacognitive instructions might improve eyewitness identification accuracy. We used a continuous dual-process model of recognition to explain familiarity-based identification errors and develop a modified lineup procedure that increased discriminability. In four studies using a multiple lineup paradigm we compared identification performance between lineup procedures featuring differing decision types (standard simultaneous, delayed-choice, elimination) and instructions (standard, metacognitive). Metacognitive instructions about how to better evaluate memory quality improved discriminability in delayed-choice but not standard or elimination lineups. With modified simultaneous lineup procedures, metacognitive instructions could potentially enable participants to use recollection more effectively and increase accuracy even when memory is poor. While immediate post-decision confidence is a good predictor of identification accuracy, lineup modifications that improve eyewitness memory use could provide more diagnostic evidence of probable guilt across a wider range of decisions. We discuss implications for lineup theory and design.

Eyewitness Science and the Call for Double-Blind Lineup Administration

For several decades, social scientists have investigated variables that can influence the accuracy of eyewitnesses’ identifications. This research has been fruitful and led to many recommendations to improve lineup procedures. Arguably, the most crucial reform social scientists advocate is double-blind lineup administration: lineups should be administered by a person who does not know the identity of the suspect. In this paper, we briefly review the classic research on expectancy effects that underlies this procedural recommendation. Then, we discuss the eyewitness research, illustrating three routes by which lineup administrators’ expectations can bias eyewitness identification evidence: effects on eyewitnesses’ identification decisions, effects on eyewitnesses’ identification confidence, and effects on administrator records of the lineup procedure. Finally, we discuss the extent to which double-blind lineup administration has been adopted among police jurisdictions in the United States and address common concerns about implementing a double-blind standard.