Publications by authors named "Gary L Wells"

The development of forensic DNA testing has led to the discovery of hundreds of cases of mistaken eyewitness identification in which innocent people were convicted. Although these discoveries of wrongful convictions from mistaken identification based on DNA testing have been a surprise and shock to the legal system and the public, psychological scientists have been less surprised. This is because psychological scientists were "blowing the whistle" on the eyewitness identification problem for decades prior to forensic DNA testing. Today, most law enforcement agencies in the United States have adopted reformed policies and procedures on eyewitness identification that are based on research by experimental social and cognitive psychologists. This article describes core aspects of this research and how the research has managed to have this impact on the U.S. legal system. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

The conceptual frameworks provided by both the lineups-as-experiments analogy and signal detection theory have proven important to understanding how eyewitness lineups work. The lineups-as-experiments analogy proposes that when investigators use a lineup procedure, they are acting as experimenters and should therefore follow the same tried-and-true procedures that experimenters follow when executing an experiment. Signal detection theory offers a framework for distinguishing between factors that improve the trade-off between culprit and innocent-suspect identifications and factors that affect the frequency of suspect identifications. We integrate these two conceptual frameworks. We argue that an eyewitness lineup procedure is characterized by two simultaneous signal detection tasks. On one hand, the witness is tasked with determining whether the culprit is present in the lineup and identifying that person. On the other hand, the investigator knows which lineup member is the suspect and which lineup members are known-innocent fillers and is therefore tasked only with determining whether the suspect is the culprit. The investigator uses the witness's identification decision and associated level of confidence to decide whether the suspect is the culprit. We leverage this realization to demonstrate a method for creating full receiver operating characteristic curves for eyewitness lineup procedures.

Objective: The Executive Committee of the American Psychology-Law Society (Division 41 of the American Psychological Association) appointed a subcommittee to update the influential 1998 scientific review paper on guidelines for eyewitness identification procedures.

Method: This was a collaborative effort by six senior eyewitness researchers, who all participated in the writing process. Feedback from members of AP-LS and the legal communities was solicited over an 18-month period.

Results: The results yielded nine recommendations for planning, designing, and conducting eyewitness identification procedures. Four of the recommendations were from the 1998 article and concerned the selection of lineup fillers, prelineup instructions to witnesses, the use of double-blind procedures, and collection of a confidence statement. The additional five recommendations concern the need for law enforcement to conduct a prelineup interview of the witness, the need for evidence-based suspicion before conducting an identification procedure, video-recording of the entire procedure, avoiding repeated identification attempts with the same witness and same suspect, and avoiding the use of showups when possible and improving how showups are conducted when they are necessary.

Conclusions: The reliability and integrity of eyewitness identification evidence is highly dependent on the procedures used by law enforcement for collecting and preserving the eyewitness evidence. These nine recommendations can advance the reliability and integrity of the evidence. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

We examined how giving eyewitnesses a weak recognition experience impacts their identification decisions. In 2 experiments we forced a weak recognition experience for lineups by impairing either encoding or retrieval conditions. In Experiment 1 ( = 245), undergraduate participants were randomly assigned to watch either a clear or a degraded culprit video and then viewed either a culprit-present or culprit-removed lineup identification procedure. In Experiment 2 ( = 227), all participants watched the same clear culprit video but were then randomly assigned to either view a clear or noise-degraded lineup procedure. Half of the participants viewed a culprit-present lineup procedure and the remaining participants viewed a culprit-removed lineup procedure. Not surprisingly, degrading either encoding or retrieval conditions led to a sharp drop in culprit identifications. Critically, and as predicted, degrading either encoding or retrieval conditions also led to a sharp increase in the identification of innocent persons. These results suggest that when a lineup procedure gives a witness a weak match-to-memory experience, the witness will lower her criterion for making an affirmative identification decision. This pattern of results is troubling because it suggests that witnesses who encounter lineups that do not include the culprit might have a tendency to use a lower criterion for identification than do witnesses who encounter lineups that actually include the culprit. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Perpetrators often wear disguises like ski masks to hinder subsequent identification by witnesses or law enforcement officials. In criminal cases involving a masked perpetrator, the decision of whether and how to administer a lineup often rests on the investigating officer. To date, no evidence-based recommendations are available for eyewitness identifications of a masked perpetrator. In 4 experiments, we examined lineup identification performance depending on variations in both encoding (studying a full face vs. a partial/masked face) and retrieval conditions (identifying a target from a full-face lineup vs. a partial/masked-face lineup). In addition, we manipulated whether the target was present or absent in the lineup in Experiments 3 and 4. Across all experiments, when participants had encoded a masked face, the masked-face lineup increased identification accuracy relative to the full-face lineup. These data provide preliminary evidence that matching lineup construction to how witnesses originally encoded the perpetrator may enhance the accuracy of eyewitness identifications. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

The present article focuses on a utility-based understanding of criminal justice practice regarding eyewitness identifications. We argue that there are 4 distinct types of utility that should be considered when evaluating an identification procedure. These include the utility associated with all identifications, the utility associated with only the high confidence identifications, the average utility across the full range of identifications, and the maximum utility that can be attained by selecting an ideal criterion. We show that in almost all cases in which the difference between 2 procedures is defined by a tradeoff between increased guilty suspect IDs and increased innocent suspect IDs, current ROC (receiver operating characteristic) curve approaches fail to provide unambiguous information about which eyewitness identification procedures are best in practice. We introduce a novel graphical technique called utility difference curves that illustrates the impact that differential assumptions about base rates and cost structures have on the likely benefits of different identification procedures. The research emphasizes the importance of considering assumptions about base rates and costs associated with different types of eyewitness errors. We also clarify situations in which the outcome of eyewitness experiments are unambiguous and those in which careful consideration of tradeoffs are necessary. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Forensic examiners are often exposed to contextual information that can bias their conclusions about evidence samples (e.g., fingerprints, fibers, tool marks). We tested the recently proposed filler-control method for moderating the biasing effects of contextual information for forensic comparisons. Borrowing from an analogy to eyewitness lineups versus showups, the filler-control method embeds a suspect's sample among known-innocent samples rather than the standard practice of presenting the analyst with only the suspect's sample for comparison. Our test of the filler-control method used fingerprints. After brief training, 234 participants compared eight sets of fingerprints in which suspect prints either matched the crime print or not, the prints were high or low in ambiguity, there was or was not contextual information suggesting there should be a match, and the suspect print was either embedded among filler prints or presented alone. Although the filler-control procedure reduced both hits and false alarms, the filler-control procedure produced better results overall as measured by ' analyses on suspect samples. These findings suggest the filler-control procedure should be considered for use in everyday forensic examination judgments, particularly when the error rate for a technique is unknown, or the risk of contextual bias is obvious, such as when examiners are called to make verification decisions. (PsycINFO Database Record

We tested the proposition that when eyewitnesses find it difficult to recognize a suspect (as in a culprit-absent showup), eyewitnesses accept a weaker match to memory for making an identification. We tie this proposition to the basic recognition memory literature, which shows people use lower decision criteria when recognition is made difficult so as to not miss their chance of getting a hit on the target. We randomly assigned participant-witnesses (N = 610) to a condition in which they were told that if they did not believe the suspect was the culprit, they would have additional opportunities to make an identification later (additional-opportunities instruction). We fully crossed this instruction with the standard admonition (i.e., the culprit may or may not be present) and with the presence or absence of the culprit in a showup identification procedure. The standard admonition had no impact on eyewitness decision-making; however, the additional-opportunities instruction reduced innocent-suspect identifications (from 33% to 15%) to a greater extent than culprit identifications (57% to 51%). The additional-opportunities instruction yielded a better tradeoff between culprit and innocent-suspect identifications as indicated by binary logistic regression and receiver operator characteristic (ROC) analyses. (PsycINFO Database Record

The U.S. legal system increasingly accepts the idea that the confidence expressed by an eyewitness who identified a suspect from a lineup provides little information as to the accuracy of that identification. There was a time when this pessimistic assessment was entirely reasonable because of the questionable eyewitness-identification procedures that police commonly employed. However, after more than 30 years of eyewitness-identification research, our understanding of how to properly conduct a lineup has evolved considerably, and the time seems ripe to ask how eyewitness confidence informs accuracy under more pristine testing conditions (e.g., initial, uncontaminated memory tests using fair lineups, with no lineup administrator influence, and with an immediate confidence statement). Under those conditions, mock-crime studies and police department field studies have consistently shown that, for adults, (a) confidence and accuracy are strongly related and (b) high-confidence suspect identifications are remarkably accurate. However, when certain non-pristine testing conditions prevail (e.g., when unfair lineups are used), the accuracy of even a high-confidence suspect ID is seriously compromised. Unfortunately, some jurisdictions have not yet made reforms that would create pristine testing conditions and, hence, our conclusions about the reliability of high-confidence identifications cannot yet be applied to those jurisdictions. However, understanding the information value of eyewitness confidence under pristine testing conditions can help the criminal justice system to simultaneously achieve both of its main objectives: to exonerate the innocent (by better appreciating that initial, low-confidence suspect identifications are error prone) and to convict the guilty (by better appreciating that initial, high-confidence suspect identifications are surprisingly accurate under proper testing conditions).

Receiver Operating Characteristic (ROC) analysis has recently come in vogue for assessing the underlying discriminability and the applied utility of lineup procedures. Two primary assumptions underlie recommendations that ROC analysis be used to assess the applied utility of lineup procedures: (a) ROC analysis of lineups measures underlying discriminability, and (b) the procedure that produces superior underlying discriminability produces superior applied utility. These same assumptions underlie a recently derived diagnostic-feature detection theory, a theory of discriminability, intended to explain recent patterns observed in ROC comparisons of lineups. We demonstrate, however, that these assumptions are incorrect when ROC analysis is applied to lineups. We also demonstrate that a structural phenomenon of lineups, differential filler siphoning, and not the psychological phenomenon of diagnostic-feature detection, explains why lineups are superior to showups and why fair lineups are superior to biased lineups. In the process of our proofs, we show that computational simulations have assumed, unrealistically, that all witnesses share exactly the same decision criteria. When criterial variance is included in computational models, differential filler siphoning emerges. The result proves dissociation between ROC curves and underlying discriminability: Higher ROC curves for lineups than for showups and for fair than for biased lineups despite no increase in underlying discriminability. (PsycINFO Database Record

A showup is an identification procedure in which a lone suspect is presented to the eyewitness for an identification attempt. Showups are commonly used when law enforcement personnel locate a suspect near the scene of a crime in both time and space but lack probable cause to make an arrest. If an eyewitness rejects a suspect from a showup, law enforcement personnel might find another suspect and run another showup. Indeed, law enforcement personnel might go through several iterations of finding suspects and running showups with the same eyewitness. We label this phenomenon the iterative-showup procedure. The consequence of this procedure is that innocent suspect identifications increase disproportionately to culprit identifications. This happens because there is only one culprit, but a seemingly endless supply of innocent suspects. We apply Bayesian modeling to single- and iterative-showup procedures to demonstrate that iterative showups are almost always associated with lower probative value. We demonstrate that the prior probabilities that later suspects are the culprit are greatly constrained by the posterior probabilities that earlier suspects were the culprit. Identifications from iterative-showup procedures are of questionable reliability. We review alternative investigative strategies that police might consider in order to limit the use of iterative-showup procedures. (PsycINFO Database Record

We provide a novel Bayesian treatment of the eyewitness identification problem as it relates to various system variables, such as instruction effects, lineup presentation format, lineup-filler similarity, lineup administrator influence, and show-ups versus lineups. We describe why eyewitness identification is a natural Bayesian problem and how numerous important observations require careful consideration of base rates. Moreover, we argue that the base rate in eyewitness identification should be construed as a system variable (under the control of the justice system). We then use prior-by-posterior curves and information-gain curves to examine data obtained from a large number of published experiments. Next, we show how information-gain curves are moderated by system variables and by witness confidence and we note how information-gain curves reveal that lineups are consistently more proficient at incriminating the guilty than they are at exonerating the innocent. We then introduce a new type of analysis that we developed called base rate effect-equivalency (BREE) curves. BREE curves display how much change in the base rate is required to match the impact of any given system variable. The results indicate that even relatively modest changes to the base rate can have more impact on the reliability of eyewitness identification evidence than do the traditional system variables that have received so much attention in the literature. We note how this Bayesian analysis of eyewitness identification has implications for the question of whether there ought to be a reasonable-suspicion criterion for placing a person into the jeopardy of an identification procedure.

Eyewitnesses (494) to actual crimes in 4 police jurisdictions were randomly assigned to view simultaneous or sequential photo lineups using laptop computers and double-blind administration. The sequential procedure used in the field experiment mimicked how it is conducted in actual practice (e.g., using a continuation rule, witness does not know how many photos are to be viewed, witnesses resolve any multiple identifications), which is not how most lab experiments have tested the sequential lineup. No significant differences emerged in rates of identifying lineup suspects (25% overall) but the sequential procedure produced a significantly lower rate (11%) of identifying known-innocent lineup fillers than did the simultaneous procedure (18%). The simultaneous/sequential pattern did not significantly interact with estimator variables and no lineup-position effects were observed for either the simultaneous or sequential procedures. Rates of nonidentification were not significantly different for simultaneous and sequential but nonidentifiers from the sequential procedure were more likely to use the "not sure" response option than were nonidentifiers from the simultaneous procedure. Among witnesses who made an identification, 36% (41% of simultaneous and 32% of sequential) identified a known-innocent filler rather than a suspect, indicating that eyewitness performance overall was very poor. The results suggest that the sequential procedure that is used in the field reduces the identification of known-innocent fillers, but the differences are relatively small.

This research examined whether confirming postidentification feedback following a mistaken identification impairs eyewitness memory for the original culprit. We also examined whether the degree of similarity between a mistakenly identified individual and the actual culprit plays a role in memory impairment. Participant-witnesses (N = 145) made mistaken identifications from a "similar" or a "dissimilar" culprit-absent photo lineup. The similar lineup contained individuals who were similar in appearance to the actual culprit and the dissimilar lineup contained individuals who were dissimilar in appearance to the actual culprit. After their identifications, witnesses were given confirming feedback ("Good job! You identified the suspect.") or no feedback. The experimenter then feigned having accidentally given the witnesses the wrong photo lineup. After telling witnesses to disregard whatever they saw in the first lineup, the experimenter gave witnesses the "correct" (culprit-present) lineup and told the witnesses to do their best to identify the culprit. Identifying a dissimilar individual and receiving confirming feedback after a misidentification had independent impairing effects on memory for the original culprit. Results extend the traditional conceptualization of the postidentification feedback effect by showing that confirming feedback not only distorts witnesses' retrospective self-reports, but it also impairs recognition memory for the culprit.

Giving confirming feedback to mistaken eyewitnesses has robust distorting effects on their retrospective judgments (e.g., how certain they were, their view, etc.). Does feedback harm evaluators' abilities to discriminate between accurate and mistaken identification testimony? Participant-witnesses to a simulated crime made accurate or mistaken identifications from a lineup and then received confirming feedback or no feedback. Each then gave videotaped testimony about their identification, and a new sample of participant-evaluators judged the accuracy and credibility of the testimonies. Among witnesses who were not given feedback, evaluators were significantly more likely to believe the testimony of accurate eyewitnesses than they were to believe the testimony of mistaken eyewitnesses, indicating significant discrimination. Among witnesses who were given confirming feedback, however, evaluators believed accurate and mistaken witnesses at nearly identical rates, indicating no ability to discriminate. Moreover, there was no evidence of overbelief in the absence of feedback whereas there was significant overbelief in the confirming feedback conditions. Results demonstrate that a simple comment following a witness' identification decision ("Good job, you got the suspect") can undermine fact-finders' abilities to discern whether the witness made an accurate or a mistaken identification.

We examined whether post-identification feedback and suspicion affect accurate eyewitnesses. Participants viewed a video event and then made a lineup decision from a target-present photo lineup. Regardless of accuracy, the experimenter either, informed participants that they made a correct lineup decision or gave no information regarding their lineup decision. Immediately following the lineup decision or after a 1-week delay, a second experimenter gave some of the participants who received confirming feedback reason to be suspicious of the confirming feedback. Following immediately after the confirming feedback, accurate witnesses did not demonstrate certainty inflation. However, after a delay accurate witnesses did demonstrate certainty inflation typically associated with confirming feedback. The suspicion manipulation only affected participants' certainty when the confirming feedback created certainty inflation. The results lend support to the accessibility interpretation of the post-identification feedback effect and the erasure interpretation of the suspicion effect.

Research-based reforms for collecting eyewitness identification evidence (e.g., unbiased pre-lineup instructions, double-blind administration) have been proposed by psychologists and adopted in increasing numbers of jurisdictions across the United States. It is well known that reducing rates of mistaken identifications can also reduce accurate identification rates (hits). But the reforms are largely designed to reduce the suggestiveness of the procedures they are meant to replace. Accordingly, we argue that it is misleading to label any hits obtained because of suggestive procedures as "hits" and then saddle reforms with the charge that they reduce the rate of these illegitimate hits. Eyewitness identification evidence should be based solely on the independent memory of the witness, not aided by biased instructions, cues from lineup administrators, or the use of lineup fillers who make the suspect stand out. Failure to call out these hits as being illegitimate can give solace to those who are motivated to preserve the status quo.

Drawing on the psychological principle that proximal consequences influence behavior more strongly than distal consequences, the authors tested the hypothesis that criminal suspects exhibit a short-sightedness during police interrogation that increases their risk for confession. Consistent with this hypothesis, Experiment 1 showed that participants (N = 81) altered how frequently they admitted to criminal and unethical behaviors during an interview to avoid a proximal consequence even though doing so increased their risk of incurring a distal consequence. Experiment 2 (N = 143) yielded the same pattern, but with a procedure that reversed the order of the proximal and distal consequences, thereby ruling out the possibility that it was the unique characteristics of the consequences rather than their proximity that influenced the admission rate. The authors discuss the supported psychological process as a potential explanation for several well-established findings reported in the literature on confessions.

Recent research in decision-making has demonstrated the "dud-alternative effect"--the tendency to become more confident that a chosen response option is correct if it is surrounded by implausible response options (Windschitl & Chambers, J Exp Psychol 30:198-215, 2004). This finding may be applicable to a lineup task: The presence of duds (i.e., highly dissimilar fillers) may increase a witness's confidence that an identified (non-dud) lineup member is the criminal. Four studies (N = 665) demonstrate that the mere presence of highly dissimilar fillers inflates witnesses' confidence in a mistaken identification (Studies 1-4), provides evidence that this confidence inflation is due to the duds inflating the perceived similarity of the other lineup members to the criminal (Studies 2, 3), and delineates some conditions under which the effect holds (Studies 3, 4). The addition of highly dissimilar lineup members, far from being inert, as is often implicitly assumed, can bias witnesses' confidence reports.

There is broad consensus among researchers both that faces are processed more holistically than other objects and that this type of processing is beneficial. We predicted that holistic processing of faces also involves a cost, namely, a diminished ability to localize change. This study (N = 150) utilized a modified change-blindness paradigm in which some trials involved a change in one feature of an image (nose, chin, mouth, hair, or eyes for faces; chimney, porch, window, roof, or door for houses), whereas other trials involved no change. People were better able to detect the occurrence of a change for faces than for houses, but were better able to localize which feature had changed for houses than for faces. Half the trials used inverted images, a manipulation that disrupts holistic processing. With inverted images, the critical interaction between image type (faces vs. houses) and task (change detection vs. change localization) disappeared. The results suggest that holistic processing reduces change-localization abilities.

Feedback suggestive of mistaken eyewitnesses claiming that they identified the correct person leads to distorted retrospective judgments of certainty, view, and other testimony-relevant measures. This feedback effect can be significantly mitigated if witnesses later learn that the feedback source did not know which lineup member was the correct person and had a manipulative intent (post-feedback suspicion manipulation). We replicated the post-feedback suspicion effect and used a mistake condition showing that the manipulative intent is not a necessary component, thereby ruling out reactance-type interpretations of the post-feedback suspicion effect. Some conditions included instructions to ensure relevant processing of the feedback before the post-feedback suspicion manipulations, but these processing instructions did not mitigate the effect. The results suggest that these retrospective judgments (e.g., certainty, attention, view) remain malleable as new information unfolds.

Real-world eyewitnesses are often asked whether their lineup responses were affected by various external influences, but it is unknown whether they can accurately answer these types of questions. The witness-report-of-influence mental-correction model is proposed to explain witnesses' reports of influence. Two experiments used a new paradigm (the actual/counterfactual paradigm) to examine eyewitnesses' abilities to report accurately on the influence of lineup manipulations. Eyewitnesses were administered either confirming feedback or no feedback (Experiment 1, n = 103), or a cautionary instruction or no cautionary instruction (Experiment 2, n = 114). Eyewitnesses then gave actual responses (retrospective confidence, view, and attention measures in Experiment 1; identification decision in Experiment 2) as well as counterfactual responses stating how they would have responded in the alternative condition. Results across both studies showed an asymmetric estimation of influence pattern: Eyewitnesses who received an influencing manipulation estimated significantly less of a change in their responses than eyewitnesses who did not receive an influencing manipulation. A 48-hr delay between actual and counterfactual responses did not moderate any effects. Results are explained by witnesses' implicit theories of influence.

The U.S. Supreme Court's ruling concerning suggestive eyewitness identification procedures (Manson v. Braithwaite, 1977, 432 U.S. 98) has not been revisited by the Court in the intervening 30+ years. Meanwhile, scientific studies of eyewitnesses have progressed and DNA exonerations show that mistaken identification is the primary cause of convictions of the innocent. We analyzed the two-inquiry logic in Manson in light of eyewitness science. Several problems are discussed. Ironically, we note that suggestive identification procedures (determined in the first inquiry) boost the eyewitnesses' standing on three of the five criteria (used in the second inquiry) that are used to decide whether the suggestive procedures were a problem. The net effect undermines safeguards intended by the Court and destroys incentives to avoid suggestive procedures.

It is not uncommon for there to be multiple eyewitnesses to a crime, each of whom is later shown a lineup. How is the probative value, or diagnosticity, of such multiple-witness identifications to be evaluated? Previous treatments have focused on the diagnosticity of a single eyewitness's response to a lineup (Wells and Lindsay, Psychol. Bull. 3 (1980) 776); however, the results of eyewitness identification experiments indicate that the responses of multiple independent witnesses may often be inconsistent. The present paper calculates response diagnosticity for multiple witnesses and shows how diagnostic probabilities change across various combinations of consistent and inconsistent witness responses. Multiple-witness diagnosticity is examined across variation in the conditions of observation, lineup composition, and lineup presentation. In general, the diagnostic probabilities of guilt were shown to increase with the addition of suspect identifications and decrease with the addition of nonidentifications. Foil identification results were more complicated-diagnostic of innocence in many cases, but nondiagnostic or diagnostic of innocence in biased lineups. These analyses illustrate the importance of securing clear records of all witness responses, rather than myopically focusing on the witness who identified the suspect while ignoring those witnesses who did not.

The Illinois pilot program on lineup procedures has helped sharpen the focus on the types of controls that are needed in eyewitness field experiments and the limits that exist for interpreting outcome measures (rates of suspect and filler identifications). A widely-known limitation of field experiments is that, unlike simulated crime experiments, the guilt or innocence of the suspects is not easily known independently of the behavior of the eyewitnesses. Less well appreciated is that the rate of identification of lineup fillers, although clearly errors, can be a misleading measure if the filler identification rate is used to assess which of two or more lineup procedures is the better procedure. Several examples are used to illustrate that there are clearly improper procedures that would yield fewer identifications of fillers than would their proper counterparts. For example, biased lineup structure (e.g., using poorly matched fillers) as well as suggestive lineup procedures (that can result from non-blind administration of lineups) would reduce filler identification errors compared to unbiased and non-suggestive procedures. Hence, under many circumstances filler identification rates can be misleading indicators of preferred methods. Comparisons of lineup procedures in future field experiments will not be easily accepted in the absence of double-blind administration methods in all conditions plus true random assignment to conditions.

Two experiments examined children's metacognitive monitoring of recognition judgments within an eyewitness identification paradigm. A confidence-accuracy (CA) calibration approach was used to examine patterns of calibration, over-/underconfidence, and resolution. In Experiment 1, children (n=619, mean age=11 years 10 months) and adults (n=600) viewed a simulated crime and attempted two separate identifications from 8-person target-present or target-absent lineups given lineup instructions that manipulated witnesses choosing patterns by varying the degree of social pressure. For choosers, but not nonchoosers, meaningful CA relations were observed for adults but not for children. Experiment 2 tested a guided hypothesis disconfirmation manipulation designed to improve the realism of children's metacognitive judgments. Children (N=796, mean age=11 years 11 months) in experimental and control conditions viewed a crime and attempted two separate identifications. The manipulation had minimal impact on the CA relation for choosers and nonchoosers. In contrast to adults, children's identification confidence provides no useful guide for investigators about the likely guilt or innocence of a suspect. These experiments revealed limitations in children's metacognitive monitoring processes that have not been apparent in previous research on recall and recognition with younger children.

The criminal justice system relies heavily on eyewitnesses to determine the facts surrounding criminal events. Eyewitnesses may identify culprits, recall conversations, or remember other details. An eyewitness who has no motive to lie is a powerful form of evidence for jurors, especially if the eyewitness appears to be highly confident about his or her recollection. In the absence of definitive proof to the contrary, the eyewitness's account is generally accepted by police, prosecutors, judges, and juries. However, the faith the legal system places in eyewitnesses has been shaken recently by the advent of forensic DNA testing. Given the right set of circumstances, forensic DNA testing can prove that a person who was convicted of a crime is, in fact, innocent. Analyses of DNA exoneration cases since 1992 reveal that mistaken eyewitness identification was involved in the vast majority of these convictions, accounting for more convictions of innocent people than all other factors combined. We review the latest figures on these DNA exonerations and explain why these cases can only be a small fraction of the mistaken identifications that are occurring. Decades before the advent of forensic DNA testing, psychologists were questioning the validity of eyewitness reports. Hugo Münsterberg's writings in the early part of the 20th century made a strong case for the involvement of psychological science in helping the legal system understand the vagaries of eyewitness testimony. But it was not until the mid- to late 1970s that psychologists began to conduct programmatic experiments aimed at understanding the extent of error and the variables that govern error when eyewitnesses give accounts of crimes they have witnessed. Many of the experiments conducted in the late 1970s and throughout the 1980s resulted in articles by psychologists that contained strong warnings to the legal system that eyewitness evidence was being overvalued by the justice system in the sense that its impact on triers of fact (e.g., juries) exceeded its probative (legal-proof) value. Another message of the research was that the validity of eyewitness reports depends a great deal on the procedures that are used to obtain those reports and that the legal system was not using the best procedures. Although defense attorneys seized on this nascent research as a tool for the defense, it was largely ignored or ridiculed by prosecutors, judges, and police until the mid 1990s, when forensic DNA testing began to uncover cases of convictions of innocent persons on the basis of mistaken eyewitness accounts. Recently, a number of jurisdictions in the United States have implemented procedural reforms based on psychological research, but psychological science has yet to have its fullest possible influence on how the justice system collects and interprets eyewitness evidence. The psychological processes leading to eyewitness error represent a confluence of memory and social-influence variables that interact in complex ways. These processes lend themselves to study using experimental methods. Psychological science is in a strong position to help the criminal justice system understand eyewitness accounts of criminal events and improve their accuracy. A subset of the variables that affect eyewitness accuracy fall into what researchers call system variables, which are variables that the criminal justice system has control over, such as how eyewitnesses are instructed before they view a lineup and methods of interviewing eyewitnesses. We review a number of system variables and describe how psychological scientists have translated them into procedures that can improve the probative value of eyewitness accounts. We also review estimator variables, variables that affect eyewitness accuracy but over which the system has no control, such as cross-race versus within-race identifications. We describe some concerns regarding external validity and generalization that naturally arise when moving from the laboratory to the real world. These include issues of base rates, multicollinearity, selection effects, subject populations, and psychological realism. For each of these concerns, we briefly note ways in which both theory and field data help make the case for generalization.

Composite faces built by eyewitnesses commonly are poor likenesses of the target face. When there are multiple witnesses, however, an opportunity exists to morph the composites. Morphs were rated as more similar to the target face than were the mean ratings of the individual composites. However, as hypothesized, the morph also came to resemble non-target faces more than the individual composites did (a prototype effect). This prototype effect was so strong that the morphs resembled non-targets more than the individual composites resembled the targets. In addition, morphing composites produced an attractiveness bias, which made the morphing of composites less effective for less attractive targets. Even when the prototype effect and the attractiveness bias were controlled for, however, a true morph-superiority effect continued to exist.

The Department of Justice's Guide for lineups recommends warning eyewitnesses that the culprit's appearance might have changed since the time of the crime. This appearance-change instruction (ACI) has never been empirically tested. A video crime with four culprits was viewed by 289 participants who then attempted to identify the culprits from four 6-person arrays that either included or did not include the culprit. Participants either received the ACI or not and all were warned that the culprit might or might not be in the arrays. The culprits varied in how much their appearance changed from the video to their lineup arrays, but the ACI did not improve identification decisions for any of the lineups. Collapsed over the four culprits, the ACI increased false alarms and filler identifications but did not increase culprit identifications. The ACI reduced confidence and increased response latency. Two processes that could account for these results are discussed, namely a decision criterion shift and a general increase in ecphoric similarity.