Lineup Size Research Articles

The effect of lineup size on discriminability is dependent on filler similarity and independent of encoding strength.

A photo lineup, which consists of one suspect and several physically similar fillers, is often used by the police to test an eyewitness's memory. To optimize memory performance, how similar should the fillers be to the suspect, and how many fillers should be included in the lineup? Recent work suggests that using fillers who match the basic characteristics of the perpetrator (e.g., same age, race, and gender) but who are otherwise maximallydissimilarto the suspect optimizes discriminability. However, the optimal lineup size has been found to vary with filler similarity, with larger lineup sizes increasing or decreasing discriminability depending on whether low-similarity or high-similarity fillers were used, respectively. Because manipulating filler similarity at retrieval affects overall performance, here we investigated whether encoding manipulations that affect overall performance also affect how lineup size influences discriminability. In three experiments, we first replicated prior findings (N = 502), then reduced encoding strength by making study images blurry when low-similarity fillers were used (N = 553), and finally increased encoding strength by repeating study images when high-similarity fillers were used (N = 501). We found that whether overall performance was low or high due these encoding manipulations, discriminability still increased as a function of lineup size when low-similarity fillers were used and decreased as a function of lineup size when high-similarity fillers were used. Thus, lineup size has opposing effects on discriminability when task difficulty is manipulated at retrieval, which narrows the theoretical explanations for why that effect is observed.

The effects of filler similarity and lineup size on eyewitness identification.

A photo lineup, which is a cross between an old/new and a forced-choice recognition memory test, consists of one suspect, whose face was either seen before or not, and several physically similar fillers. First, the participant/witness must decide whether the person who was previously seen is present (old/new) and then, if present, choose the previously seen target (forced choice). Competing signal-detection models of eyewitness identification performance make different predictions about how certain variables will affect a witness's ability to discriminate previously seen (guilty) suspects from new (innocent) suspects. One key variable is the similarity of the fillers to the suspect in the lineup, and another key variable is the size of the lineup (i.e., the number of fillers). Previous research investigating the role of filler similarity has supported one model, known as the Ensemble model, whereas previous research investigating the role of lineup size has supported a competing model, known as the Independent Observations model. We simultaneously manipulated these two variables (filler similarity and lineup size) and found a pattern that is not predicted by either model. When the fillers were highly similar to the suspect, increasing lineup size reduced discriminability, but when the fillers were dissimilar to the suspect, increasing lineup size enhanced discriminability. The results suggest that each additional filler adds noise to the decision-making process and that this noise factor is minimized by maximizing filler dissimilarity. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

The effects of lineup size on the processes underlying eyewitness decisions

Here we apply the two-high threshold eyewitness identification model to identify the effects of lineup size on the detection-based and non-detection-based processes underlying eyewitness decisions. In Experiment 1, lineup size was manipulated by showing participants simultaneous or sequential lineups that contained either three or six persons. In Experiment 2, the lineups contained either two or five persons. In both experiments, the culprit was better detected in smaller than in larger lineups. Furthermore, participants made fewer guessing-based selections in smaller than in larger lineups. However, guessing-based selection in larger lineups was not increased to a level sufficient to offset the effect of increased protection of suspects in larger lineups due to the fact that the guessing-based selections that occur are distributed across more persons. The results show that increasing the lineup size causes several changes in the detection-based and non-detection-based processes underlying eyewitness decisions.

Lineup size influences voice identification accuracy

AbstractWe investigated the effects of lineup size, target presence, and target sex on voice identification accuracy. In Study 1, participants identified a female target from 1‐, 6‐, or 10‐voice target present or target absent lineups. Results demonstrated increasing accuracy with smaller target absent lineups. One‐voice lineups led to higher rates of innocent suspect identifications than 10‐voice lineups. In Study 2, participants identified a male or female target from 1‐, 6‐, or 10‐voice target present or target absent lineups. Results revealed increased correct identifications in 1‐ and 6‐voice and increased innocent suspect identifications in 1‐voice lineups, compared to 10‐voice lineups. Female lineups resulted in higher accuracy in target present lineups yet increased rates of innocent suspect identifications. Our findings indicate 1‐voice lineups result in both increased accuracy and increased innocent suspect identifications, a trade‐off which may not be advisable. Future research should further explore the impact of multi‐voice lineups on accuracy.

A stronger memory for the perpetrator may attenuate effects of the identification procedure on eyewitness accuracy

AbstractThe 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.

A meta-analysis of lineup size effects on eyewitness identification.

A meta-analysis of lineup size effects on eyewitness identification.

The effect of lineup size on eyewitness identification.

Eyewitness identification via lineup procedures is an important and widely used source of evidence in criminal cases. However, the scientific literature provides inconsistent guidance on a very basic feature of lineup procedure: lineup size. In two experiments, we examined whether the number of fillers affects diagnostic accuracy in a lineup, as assessed with receiver-operating characteristic (ROC) analysis. Showups (identification procedures with one face) led to lower discriminability than simultaneous lineups. However, in neither experiment did the number of fillers in a lineup affect discriminability. We also evaluated competing models of decision-making from lineups. This analysis indicated that the standard Independent Observations (IO) model, which assumes a decision rule based on the comparison of memory strength signals generated by each face in a lineup, is incapable of reproducing the lower level of performance evident in showups. We could not adjudicate between the Ensemble model, which assumes a decision rule based on the comparison of the strength of each face with the mean strength across the lineup, and a newly introduced Dependent Observations model, which adopts the same decision rule as the IO model, but with correlated signals across faces. We draw lessons for users of lineup procedures and for basic research on eyewitness decision making. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Supplemental Material for A Meta-Analysis of Lineup Size Effects on Eyewitness Identification

Supplemental Material for A Meta-Analysis of Lineup Size Effects on Eyewitness Identification

The number of fillers may not matter as long as they all match the description: The effect of simultaneous lineup size on eyewitness identification

SummaryAccording 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.

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 U.S. and U.K. lineup procedures, discriminability and reliability was better when memory was tested using the U.S. 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 U.S. and U.K. lineups to determine their effects on discriminability and reliability. In 5 experiments, we compared (a) presentation format: simultaneous versus sequential; (b) stimulus format: photos versus videos; (c) number of views: 1-lap versus 2-lap versus choice in both video and photo lineups; and (d) 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. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

The impact of fillers on lineup performance

Filler siphoning theory posits that the presence of fillers (known innocents) in a lineup protects an innocent suspect from being chosen by siphoning choices away from that innocent suspect. This mechanism has been proposed as an explanation for why simultaneous lineups (viewing all lineup members at once) induces better performance than showups (one-person identification procedures). We implemented filler siphoning in a computational model (WITNESS, Clark, Applied Cognitive Psychology 17:629–654, 2003), and explored the impact of the number of fillers (lineup size) and filler quality on simultaneous and sequential lineups (viewing lineups members in sequence), and compared both to showups. In limited situations, we found that filler siphoning can produce a simultaneous lineup performance advantage, but one that is insufficient in magnitude to explain empirical data. However, the magnitude of the empirical simultaneous lineup advantage can be approximated once criterial variability is added to the model. But this modification works by negatively impacting showups rather than promoting more filler siphoning. In sequential lineups, fillers were found to harm performance. Filler siphoning fails to clarify the relationship between simultaneous lineups and sequential lineups or showups. By incorporating constructs like filler siphoning and criterial variability into a computational model, and trying to approximate empirical data, we can sort through explanations of eyewitness decision-making, a prerequisite for policy recommendations.

Evaluating lineup fairness: Variations across methods and measures.

Triers of fact sometimes consider lineup fairness when determining the suggestiveness of an identification procedure. Likewise, researchers often consider lineup fairness when comparing results across studies. Despite their importance, lineup fairness measures have received scant empirical attention and researchers inconsistently conduct and report mock-witness tasks and lineup fairness measures. We conducted a large-scale, online experiment (N = 1,010) to examine how lineup fairness measures varied with mock-witness task methodologies as well as to explore the validity and reliability of the measures. In comparison to descriptions compiled from multiple witnesses, when individual descriptions were presented in the mock-witness task, lineup fairness measures indicated a higher number of plausible lineup members but more bias toward the suspect. Target-absent lineups were consistently estimated to be fairer than target-present lineups-which is problematic because it suggests that lineups containing innocent suspects are less likely to be challenged in court than lineups containing guilty suspects. Correlations within lineup size measures and within some lineup bias measures indicated convergent validity and the correlations across the lineup size and lineup bias measures demonstrated discriminant validity. The reliability of lineup fairness measures across different descriptions was low and reliability across different sets of mock witnesses was moderate to high, depending on the measure. Researchers reporting lineup fairness measures should specify the type of description presented, the amount of detail in the description, and whether the mock witnesses viewed target-present and/or -absent lineups. (PsycINFO Database Record

Nosewitness Identification: Effects of Lineup Size and Retention Interval.

Although canine identification of body odor (BO) has been widely used as forensic evidence, the concept of nosewitness identification by human observers was only recently put to the test. The results indicated that BOs associated with male characters in authentic crime videos could later be identified in BO lineup tests well above chance. To further evaluate nosewitness memory, we assessed the effects of lineup size (Experiment 1) and retention interval (Experiment 2), using a forced-choice memory test. The results showed that nosewitness identification works for all lineup sizes (3, 5, and 8 BOs), but that larger lineups compromise identification performance in similarity to observations from eye- and earwitness studies. Also in line with previous eye- and earwitness studies, but in disagreement with some studies on odor memory, Experiment 2 showed significant forgetting between shorter retention intervals (15 min) and longer retention intervals (1-week) using lineups of five BOs. Altogether this study shows that identification of BO in a forensic setting is possible and has limits and characteristics in line with witness identification through other sensory modalities.

Does Lineup Size Matter with Child Witnesses

Children’s (N = 89) identification accuracy was examined as a function of lineup size. Participants (8–13 years) viewed a videotaped staged event, described what was witnessed and then were presented with either a target-present or—absent lineup containing 6 versus 12 lineup members. The elimination lineup procedure (Pozzulo and Lindsay J Appl Psychol 38: 2195–2209 1999) was used to present lineups. No significant differences in correct identification rates were found across the target-present sized lineups. In addition, the target was likely to “survive” at a comparable rate regardless of lineup size. Moreover, there was no significant difference in correct rejection rate as a function of lineup size. The non significance of these data are critical given that most research with child witnesses uses 6-person lineups whereas in many real world contexts larger sized lineups are used (e.g., 12-person in Canada).

Eyewitness Identification Accuracy and Response Latency.

Eyewitness identification research has reliably shown that accurate identifications are faster than inaccurate identifications. Recently, D. Dunning and S. Perretta (2002) claimed that an identification latency of 10-12 s not only best discriminates between accurate and inaccurate identifications but also produces extremely high accuracy rates, approaching 90%. Consistent with predictions from recognition memory theory, however, we show that the optimum time boundary varies with overall response latency under manipulations of retention interval and nominal lineup size, and that the accuracy rate inside the optimum time boundary is much less impressive than previously reported. We outline directions for clarifying the accuracy and latency relationship to assist the reliable diagnosis of identification accuracy.

Measures of lineup fairness: do they postdict identification accuracy?

Various measures have been proposed to test the fairness of lineups (Doob & Kirshenbaum, 1973; Malpass, 1981; Wells, Leippe and Ostrom, 1979). In three experiments, we examined the relationship of identification accuracy to measures of lineup bias (proportion of mock witness choices, defendant bias, functional size) and lineup size (effective size, number of acceptable lineup members). Lineup bias measures successfully postdict false positive choices, but only for some lineup procedures. Lineup size measures rarely postdict false positive decisions. Lineup fairness measures do not postdict false identifications from sequential lineups. Implications for measuring and reporting lineup fairness in court are discussed. Copyright © 1999 John Wiley & Sons, Ltd.

Statistical considerations when determining measures of lineup size and lineup bias

Much eyewitness research has centred on the development and evaluation of measures of lineup properties. These measures have proved useful to researchers and to expert witnesses who testify on eyewitness testimony. However, the inferential statistical properties of the measures themselves are rarely taken into account, despite the fact that most of them are derived from the mock witness task, which relies on an implicit probability model. This is a failing, and it is argued that estimates of lineup properties reported without inferential considerations may be misleading. Methods are suggested here for reasoning inferentially about lineup measures, and for planning studies to ensure adequate statistical power. Suggestions made by eyewitness researchers regarding the practical interpretation of lineup measures are critically evaluated, as are recommendations for new lineup measures, as suggested by Lindsay et al. (this issue). Copyright © 1999 John Wiley & Sons, Ltd.

Applied issues in the construction and expert assessment of photo lineups

Issues surrounding lineup fairness have been explored scientifically for over two decades. The present study investigates the applied/external validity of this line of research. First, several factors leading to bias in the construction of photo lineups are examined, and results of a preliminary survey on current law-enforcement practices are presented. Several statistics that have been developed to assess the fairness of lineups are reviewed and the application of these techniques to lineups used in 18 criminal cases is discussed, including the mixed agreement that sometimes occurs between estimates. Finally, we address the usefulness of lineup fairness assessment for expert testimony in the courtroom, and the dilemma that may be faced by the expert witness who is asked to testify by the defence. It is suggested that a useful and empirically justified index of overall lineup fairness can be created by combining a single estimate of bias (Functional Size) and a single estimate of lineup size (Effective Size) into a four-point index. Copyright © 1999 John Wiley & Sons, Ltd.

Protecting innocent defendants, nailing the guilty: a modified sequential lineup

Can the traditional lineup procedure be modified in such a way as to still secure positive identifications of guilty persons while minimizing the risk of misidentifications? Witnesses interacted with a ‘culprit’ who they were later called upon to identify from a 20-person sequential video lineup. Both culprit-present and culprit-absent lineups were employed and witnesses could choose more than one suspect. In 61 culprit-present lineups 43% chose only the suspect, while in 93 culprit-absent lineups no-one did. In culprit-present lineups 25% chose him along with foils, while 5% did so in culprit-absent lineups. Larger lineup size, and the ability to make multiple choices, helped lower the probability of choosing only an innocent suspect. Using Baysian analysis, the probability that a chosen defendant was innocent, based on the lineup alone, equalled 0.03, compared to 0.258 in traditional lineups. © 1998 John Wiley & Sons, Ltd.

Standards for Evaluating the Fairness of Photograph Lineups

In theory a lineup is fair, from the perspective of the suspect, to the extent that the suspect is not distinctive in appearance from the other lineup members (foils) and all of the foils are reasonably similar in general appearance to the suspect. Lineup fairness can be divided into two dimensions-size and bias. Several proposed methods for empirically evaluating lineup fairness were assessed in terms of their sensitivity to absolute standards of lineup fairness and their discriminability, the extent that they differentiated between lineups designed to be fair and those constructed via less rigorous selection procedures. One of three lineup size measures and both measures of lineup bias showed significant discriminability. The sensitivity of the measures depended on the criteria arbitrarily chosen or, when using statistical significance, on sample size. Race of mock witness had some impact on evaluations of Black lineups but not on evaluations of White lineups. Results indicated that a sample size of 18 ...