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The identification procedure can greatly affect eyewitness performance, but this may be contingent upon a relatively weak memory for the perpetrator. In a large preregistered experiment (N = 13,728), we manipulated memory strength and tested participants with a target-present or -absent showup or lineup (size 3 or 6). All fillers were description-matched but were of low or high similarity with the target. We replicated the advantage of fair simultaneous lineups over showups and the advantage of low- over high-similarity fillers when memory for the perpetrator's face was weaker (short exposure duration), but both effects were significantly reduced when memory was stronger. There was no effect of lineup size regardless of memory strength or filler similarity. We conclude that some recommendations to police may be more robust than others across changes in estimator variables such as memory strength and that more research is needed on interactions between estimator and system variables.

The diagnostic feature-detection theory (DFT) of eyewitness identification is based on facial information that is diagnostic versus non-diagnostic of suspect guilt. It primarily has been tested by discounting non-diagnostic information at retrieval, typically by surrounding a single suspect showup with good fillers to create a lineup. We tested additional DFT predictions by manipulating the presence of facial information (i.e., the exterior region of the face) at both encoding and retrieval with a large between-subjects factorial design (N = 19,414). In support of DFT and in replication of the literature, lineups yielded higher discriminability than showups. In support of encoding specificity, conditions that matched information between encoding and retrieval were generally superior to mismatch conditions. More importantly, we supported several DFT and encoding specificity predictions not previously tested, including that (a) adding non-diagnostic information will reduce discriminability for showups more so than lineups, and (b) removing diagnostic information will lower discriminability for both showups and lineups. These results have implications for police deciding whether to conduct a showup or a lineup, and when dealing with partially disguised perpetrators (e.g., wearing a hoodie).

Most eyewitness identification research simulates single perpetrator crimes, but real-world crimes often transpire at the hands of multiple perpetrators. It is unclear how multiple perpetrators might impact the ability of eyewitnesses to discriminate between the guilty and innocent. To address this issue, we conducted two experiments in which large nationwide samples of participants read a vignette about a crime being committed, and then viewed one to two target faces. If there were two targets, they were either similar or dissimilar, and presented either simultaneously or sequentially. Participants later viewed a target-present or -absent lineup for each target. As predicted, presenting one target enhanced discriminability compared to two targets presented simultaneously (Experiments 1 and 2), and two targets presented sequentially (Experiment 2). Results were mixed regarding the effect of similarity, with discriminability better for dissimilar compared to similar target pairs in just one experiment. Lastly, high confidence indicated high accuracy across all conditions.

Recent research indicates that mock jurors place too much weight on eyewitness confidence expressed in the courtroom rather than confidence expressed immediately after an identification, though eyewitness identification research clearly shows that only the latter is indicative of guilt. Researchers rarely present mock jurors with photo arrays, which could help them to better understand the eyewitness' point of view. Across three experiments, potential jurors viewed photo arrays and hypothetical eyewitness confidence statements described as coming either immediately after the identification or much later in the courtroom. In Experiment 1, suspect guilt was rated as more likely when immediate or courtroom confidence was high. Experiment 2 reduced suspect guilt estimates associated with high courtroom confidence by providing partial Henderson instructions. Experiment 3 replicated this effect and found that simple directives from an eyewitness identification expert were even more beneficial in helping potential jurors correctly evaluate confidence based on timing. We recommend that eyewitness experts be allowed to instruct jurors not to trust confidence expressed at trial. [ABSTRACT FROM AUTHOR]

Many crimes occur in which a perpetrator has a distinctive facial feature, such as a tattoo or black eye, but few eyewitness identification (ID) studies have involved such a feature. We conducted an experiment to determine how eyewitness ID performance is impacted by a distinctive facial feature, and how police could deal with this issue. Participants (N = 4,218) studied a target face with or without a black eye, and later viewed a simultaneous photo lineup either containing the target or not. For those who saw a target with a black eye, this feature was either replicated among all lineup members or was removed. The black eye harmed empirical discriminability regardless of replication or removal, which did not differ. However, participants responded more conservatively when the black eye was removed, compared to replication. Lastly, immediate confidence was consistently indicative of accuracy.

According to the Diagnostic Feature-Detection (DFD) hypothesis, the presence of fillers that match the eyewitness's description of the perpetrator will boost discriminability beyond a showup, and very few fillers may suffice to produce the advantage. We tested this hypothesis by comparing showups with simultaneous lineups of size 3, 6, 9, and 12. Participants (N = 10,433) were randomly assigned to one of these conditions, as well as target-present (TP) versus target-absent (TA) lineup. As predicted by the DFD hypothesis, lineups were superior to showups, and there was no advantage with increased lineup size beyond a 3-member lineup. The confidence-accuracy (CA) relationship held a similar pattern. The only effect of increased lineup size was a lower likelihood of choosing a suspect (guilty or innocent). We conclude that police should focus more on the quality rather than quantity of fillers.

The distance from which an eyewitness views a perpetrator is a critical factor for eyewitness identification, but has received little research attention. We presented three mock-crime videos to participants, varying distance to three perpetrators (3, 10, or 20 m). Across two experiments, increased distance reduced empirical discriminability in the form of a mirror effect, such that correct identifications decreased while false identifications increased. Moreover, high confidence identifications were associated with high accuracy at 3 m (Experiment 1 and 2) and 10 m (Experiment 2), but not at 20 m. We conclude that eyewitnesses may be less likely to identify a perpetrator viewed at a distance, and also more likely to falsely identify an innocent suspect. Furthermore, there may be certain boundary conditions associated with distance and the impact it has on the confidence-accuracy relationship. More research is needed to elucidate the effect of estimator variable manipulations on the confidence-accuracy relationship.

It is important to consider the two parameters of signal detection theory, discriminability and response bias, when evaluating eyewitness identification from simultaneous lineups. On the basis of the diagnostic feature-detection hypothesis, we tested a method for increasing discriminability that encourages eyewitnesses to carefully rank each lineup member based on match to their memory for a perpetrator. This procedure increased empirical discriminability and also eliminated a response bias that is largely overlooked in the literature: Participants were biased to choose from the top row of the six-pack (2 × 3) lineup commonly used in the United States. We argue that suspect position in the simultaneous lineup is an important variable to consider for researchers and the criminal justice system. We also encourage researchers to test the ranking procedure to determine if such a simple set of instructions could be utilized by police to help eyewitnesses correctly sort innocent versus guilty suspects.

It is common for a perpetrator’s appearance to change between committing the crime and later appearing in an identification procedure. The present study investigated how such appearance change (AC) would be evaluated by potential jurors, as well as tested mock jurors’ evaluations of the appearance change instruction (ACI) utilized by police. Recent research indicates that the ACI harms eyewitness identification accuracy and limits the predictive nature of confidence, but would mock jurors’ estimates of suspect guilt reflect this? In Experiment 1, AC reduced suspect guilt estimates, but the ACI eliminated this effect, indicating that potential jurors may not discount an identification if made after ACI. Experiment 2 introduced a hypothetical eyewitness expert who informs participants about the research that both AC and the ACI harm eyewitness performance. We also compared two types of expert instructions based on recent mock jury research: simple versus reason-based. Both types served to reduce suspect guilt estimates associated with AC. Participants still trusted the ACI even with expert instructions, but not as much as when there was no expert. Lastly, we also manipulated eyewitness confidence level, supporting recent research that manipulations have no effect on suspect guilt estimates when confidence is low (i.e. uncertainty trumps). [ABSTRACT FROM AUTHOR]

Based on its importance in the criminal justice system, it is critical to understand how jurors interpret eyewitness identification evidence in the form of photo arrays and witness statements. We addressed several unresolved questions, including: How do potential jurors interpret eyewitness statements regarding confidence and decision speed? Are suspect identifications from fair lineups trusted more than those from biased lineups or showups? What if the eyewitness chooses a filler or rejects the lineup? Three experiments with large demographically-diverse U.S. samples provided three novel results. First, identifications with fast statements (e.g. 'I identified him instantly.') were trusted more than identifications with slow statements (e.g. 'I recognized him after a few minutes.') unless they were supported with low confidence, when speed statement had no effect. Second, biased lineups were often not perceived as biased, but when they were, suspect identifications were not trusted. Third, neither confidence nor speed statements had any impact on judgments of suspect guilt when participants were informed that a filler was chosen or the lineup/showup was rejected. We recommend that jurors be educated regarding how to appropriately evaluate eyewitness evidence. [ABSTRACT FROM AUTHOR]