Effects of Expert Psychological Advice on Human Performance in Judging the Validity of Eyewitness Testimony

Transcription

1 Law and Human Behavior, Vol. 4, No. 4, 1980 Effects of Expert Psychological Advice on Human Performance in Judging the Validity of Eyewitness Testimony Gary L. Wells,* R. C. L. Lindsay,t and J. P. Tousignant~ A review is made of recent experimental research regarding how well human observers can judge the accuracy of eyewitness testimony. It is concluded that people: (a) may be overwilling to believe in the accuracy of eyewitnesses' memory; (b) rely too heavily on the confidence of eyewitnesses in judging the validity of testimony; (e) fail to adequately account for witnessing conditions across crimes; and (d) cannot discriminate between accurate and inaccurate witnesses within crimes. New data are reported from an experiment designed to test the effects that expert psychological advice has on subject-jurors' performance with regard to these four deficiencies. The results showed that expert advice served to eliminate the overbelief bias and greatly reduced subject-jurors' reliance on the confidence of the witnesses. Expert advice did not improve the extent to which subject-jurors took account of the witnessing conditions across crimes nor their ability to discriminate between accurate and inaccurate witnesses within crimes. INTRODUCTION It has long been argued that psychology may be successfully applied to courtroom testimony (Munsterberg, 1908). Eyewitness researchers have endorsed this argument for several good reasons. Foremost among these reasons is psychology's erudite history of experimental research in human memory. Furthering psychology's ability to contribute to matters of courtroom testimony is the more recent investigations of memory in dynamic settings such as staged crimes wherein memory is somewhat incidental and a greater appreciation for limitations in human memory is apparent. *Department of Psychology, University of Alberta, Canada.?Department of Psychology, University of Manitoba, Canada. :~Department of Psychology, University of Washington /80/ / Plenum Publishing Corporation

2 276 WELLS, LINDSAY, AND TOUSIGNANT Thus, psychologists not only have the benefit of approximately 100 years of basic empirical and theoretical work on human memory, but also have the benefit of recent experimental work that is specifically designed to address questions about how human memory is likely to function in settings of interest to the criminal justice system. Recent books by Clifford & Bull (1978), Loftus (1979), and Yarmey (1979) as well as the papers in this special issue attest to the respectable state of knowledge that now exists on eyewitness testimony. The basic mode through which psychology currently makes its contribution to courtroom testimony is through the use of expert psychologists who can "facilitate the acquisition of knowledge by the jury, or trier of fact, thus enabling them to reach a final [superior] determination" (Loftus, 1980, p. 9). In spite of the high qualifications that psychology has in the area of memory, the current role of eyewitness psychology in the courtroom has not gone unquestioned (Wells, 1978). The basic argument by Wells in 1978 was that we knew little about how adequately or inadequately triers of fact (jurors, judges) performed in their assessments of eyewitness testimony. If psychology's goal is to improve the courts' decisions in assessing eyewitness testimony, then we should first document that there is room for improvement. What is the level of human performance in judging the validity of eyewitness testimony? Fortunately, we now have some answers that did not exist as recently as 1978 and the next section of this article addresses that question. IS THERE ROOM FOR IMPROVEMENT IN HUMAN JUDGMENT OF EYEWITNESSES? There are at least three ways to approach the question of how adequately the judicial system assesses eyewitness accounts. One way is to examine the incidence of cases in which an eyewitness' false account was a determining factor in incriminating an innocent defendant. This would presumably tell us something about how the trier(s) of fact made a decisional error in having believed an inaccurate eyewitness account. Such documentation has been handled elsewhere (Brandon & Davies, 1973) and suffers from several problems. First, such incidents are brought to light almost exclusively via new evidence as a result of some completely chance occurrence. Brandon and Davies listed 70 cases and suggested that it was "the tip of a much larger iceberg" (Brandon & Davies, p. 20). This approach is further complicated by the fact that it presents only half of the necessary information; in order to assess the extent to which courts make good decisions about believing and disbelieving eyewitnesses we should also assess how often the courts disbelieve eyewitnesses whose memorial accounts are valid. A second approach to assessing the adequacy of the judicial system's performance in judging the validity of eyewitness accounts was recently undertaken by Hastie (Note 1). Hastie presented a one and a half hour film reenactment of an armed robbery trial to eleven 6-person juries obtained from a superior court jury pool. These juries then deliberated for 35 minutes to 135 minutes and the deliberations were videotaped. The evidence in the trial involved three eyewitnesses and the videotaped jury deliberations were subjected to an analysis in which all remarks concerning eyewitness identification, eyewitness reliability, and human memory were summarized verbatim and coded by judges. The results suggested that several significant issues

3 JUDGING EYEWITNESS TESTIMONY 277 were either not discussed or given cursory treatment: The possibility of selective attention and encoding by the eyewitnesses, the possibility of suggestive police behavior, possible nonindependence of the witnesses, the possibility of the witnesses adding to their memories during the retention interval, and inadequate discussion of the characteristics of the nonidentified foils in the lineup. In addition, some jurors used two hypotheses about eyewitness memory in an apparently inappropriate fashion: Some assumed that stress on the witness would improve memory and most assumed that high confidence on the part of the witness implied accuracy. An alternative approach to assessing the adequacy of the courts' performance in judging eyewitness accounts was only recently developed (Wells, Lindsay, & Ferguson, 1979). This approach uses the familiar staged crime technique in which unsuspecting witnesses later attempt to make an identification of the "criminal" from a lineup or picture array. Instead of ending the experiment at that point, however, Wells et al. carried the process further by cross-examining the eyewitnesses and had subjectjurors who viewed the cross-examination indicate whether they believed that the eyewitness had identified the true offender versus an innocent person. In effect it is analagous to a signal detection task wherein there are two types of stimuli (witnesses who have made accurate versus inaccurate identifications) and two types of responses (believing vs. disbelieving the witness). The situation, therefore, yields four possible outcomes: (a) a "hit," or a juror believing an accurate witness; (b) a "miss," or a juror disbelieving an accurate witness; (c) a "false alarm," or a juror believing an inaccurate witness; (d) a "correct rejection," or a juror disbelieving an inaccurate witness. The Wells et al. (1979) paradigm is significantly different from that used by Hastie in that the Wells et al. paradigm is designed to classify subject-jurors' decisions (about believing given eyewitnesses) as correct or incorrect decisions. Hastie's (Note 1) approach is one of examining the process by which those decisions are made and the measures have to do with the adequacy of the decision process rather than the decisional outcome. Both approaches are necessary and valuable. Our preference for the use of individual eyewitnesses to staged crimes as stimuli (rather than an entire set of trial evidence) and measuring subject-jurors' belief/disbelief decisions (rather than deliberated verdicts) stems from our interest in obtaining a "pure" measure of how well people can judge the validity of eyewitness accounts, a measure that is difficult or impossible when other evidence is also presented. It also allows us to assess the extent to which the likelihood of subject-jurors believing eyewitnesses exceeds the experimentally defined likelihood that the eyewitnesses were accurate, a phenomenon that we call "overbelief." How adequately have people performed in judging the accuracy of eyewitnesses? 1 The data have not been encouraging. Wells, Lindsay, & Ferguson (1979) staged thefts individually for 127 eyewitnesses, had the witnesses attempt an identification from a photo-lineup and then cross-examined 24 eyewitnesses who made an accurate identification of the thief and 18 eyewitnesses who identified an innocent per- 1The current article deals exclusively with how people judge the validity of eyewitness identifications. It is beyond the scope of this article to assess how people judge eyewitness recall rather than identifications. It is also beyond the scope of this article to plenarily address how people deal with "nonidentifications" by eyewitnesses (e.g., failure of eyewitness to choose anyone from a lineup). The latter issue is addressed in Wells & Lindsay (1980).

4 278 WELLS, LINDSAY, AND TOUSIGNANT son from the photo-lineup. The results showed that the subject-jurors who observed the cross examinations tended to have high belief of the witnesses (witnesses were believed 79.8% of the time), and that subject-jurors were no less likely to believe an eyewitness who had identified an innocent suspect than they were to believe an eyewitness who had identified the correct person. This suggests that human observers have absolutely no ability to sort out eyewitnesses who have mistakenly identified an innocent person. Wells et al. (1979) suggested that the reason that subject-jurors were operating at chance is because there was little or no relationship between the eyewitnesses' selfrated confidence that they were accurate and the eyewitnesses' actual accuracy. This low or nonexistent relationship between identification accuracy and confidence of eyewitnesses is discussed by Deffenbacher (1980). If the witnesses' self-rated confidence is an unreliable cue to the witnesses' accuracy, what can a juror do to assess the likely accuracy of an eyewitness? It seems only reasonable that a juror must rely on the characteristics of the witnessing situation and use such factors as the amount of time that the witness had to view the criminal's face, how much the physical characteristics of the criminal might have been visually shielded, and so on, to judge the likelihood of the eyewitness' memory being accurate. The Wells et al. study, however did not give subject-jurors the opportunity to use discriminating factors of that sort because the witnessing situation was identical for all eyewitnesses. What seemed necessary was to manipulate the characteristics of the criminal event rather than holding the nature of the event constant. In this way the subject-jurors could display their abilities to discriminate between eyewitnesses to different crime conditions rather than between eyewitnesses to the same crime. This was precisely the type of study conducted by Lindsay, Wells, & Rumpel (1981). Lindsay et al. manipulated multiple factors in a staged crime to create three levels of accuracy. In one condition the witnesess saw a theft in which the thief had a toque (hat) that covered his hair and the thief was only briefly in view of the witness (poor witnessing conditions event). In a second condition, the toque was worn higher on the thief's head, thereby increasing the amount of visual information available for witnesses to process (moderate witnessing conditions event). In the third condition the toque was never worn by the thief and the thief was visible for a longer period of time (good witnessing conditions event). These three conditions yielded 33%, 50%, and 74% accurate identifications of the thief among those who made an identification from a photo-lineup, respectively. The eyewitnesses were then cross-examined by a person who did not know whether the eyewitnesses were accurate or not. Subject-jurors then viewed the cross-examination and made belief-disbelief decisions. The Wells et al. (1979) data were replicated in the sense that within crimes (i.e., within the 33%, 50%, or 74% accuracy conditions) the subject-jurors were as likely to believe the inaccurate witnesses as they were to believe the accurate witnesses. Across crimes, however, the subject-jurors showed a tendency to reduce their belief of the eyewitnesses in the proper direction. That is, the crime that produced low accuracy (33%) yielded less belief of the eyewitnesses on the part of the subject-jurors than did the crime that produced high accuracy (74%). This was true in spite of the fact that the witnesses' confidence that they were accurate did not vary across conditions. Apparently, the subject-jurors were able to discern (via the witnesses' testimony) that the witnessing conditions were significantly poorer in the low-accuracy conditions than in the high-

5 JUDGING EYEWITNESS TESTIMONY 279 accuracy conditions. That's the good news. Now the bad news. In every condition the subject-jurors' rates of belief were higher than were the rates of witness accuracy. This was especially true when the witnessing conditions were poor, at which point subjectjurors believed witnesses 62% of the time while only 33% of the witnesses were accurate. In addition, the strong tendency for subject-jurors to show overreliance on eyewitnesses' confidence [demonstrated in Wells et al. (1979)] was also replicated. Thus, we can conclude that (a) subject-jurors cannot separate accurate from inaccurate witnesses for a given staged crime, (b) subject-jurors do not adequately account for witnessing conditions in the rate at which they believe eyewitnesses, (c) subject-jurors tend to overbelieve witnesses, especially when the witnesses were exposed to poor witnessing conditions, and (d) subject-jurors rely too heavily on eyewitness confidence in judging the validity of eyewitness accounts. These conclusions are, of course, very general and their generality may be unwarranted. It seems only reasonable to suggest that subject-jurors may not be as overbelieving of witnesses if they are given the benefit of expert advice on the matter. That is the type of issue addressed in the next section and the main concern of the current article. EFFECTS OF EXPERT PSYCHOLOGICAL ADVICE If psychologists are to enter the courts as experts on eyewitness testimony, it is only reasonable to suggest that psychologists do a thorough job in their research. This means that psychologists should not only study the nature of eyewitness memory, but also investigate the likely impact that their expert advice has on the quality of decisions rendered by the recipient of the expert advice. Here again we suggest that the Wells et al. (1979) paradigm can provide some answers by testing the impact of such advice on subject-jurors' decisions to believe accurate versus inaccurate witnesses both within a given witnessing condition and across witnessing conditions. This is not, however, the only way to assess the impact of expert advice. Loftus (1980) recently conducted two experiments in which subject-jurors read a case against a defendant and rendered a verdict under conditions of expert advice identifying several factors pertinent to the specific case (e.g., the fact that the identification was cross-racial, which is believed to be inferior to same-race identification) or without benefit of expert testimony. The dependent measures were the percentage of guilty verdicts, by jurors, and the amount of time jurors spent in discussing the eyewitness accounts. The percentage of guilty verdicts declined as a function of expert advice and the amount of attention to the eyewitness testimony was increased. This suggests that the expert advice had beneficial effects. It is not the drop in guilty verdicts per se, but rather the effect of expert advice on the amount of scrutiny that the jurors devoted to the eyewitness testimony that makes Loftus' (1980) study promising. The current authors recently conducted a study using the Wells et al. (1979) paradigm in which witnesses to staged crimes were cross-examined and subject-jurors observed the cross-examinations either with or without benefit of expert psychological advice. A comparison of this study, Loftus' (1980) study, and a study conducted by Hosch, Beck, & McIntyre (1980) is outlined in Hosch (1980). In addition to the differences among these three studies as outlined by Hosch

6 280 WELLS, LINDSAY, AND TOUSIGNANT (1980) the reader might note that our manipulation of expert advice occurred before rather than after the eyewitness testimony. This is the main reason that we refer to our manipulation as expert advice rather than expert testimony. Rarely would expert testimony precede the testimony of the eyewitness(es). Our approach reflects our philosophy and goals at the time we designed the study. Our belief is that expert psychological knowledge should occur early in the trial so that its benefits can be utilized during the testimony of the eyewitness(es) rather than 'after the eyewitness testimony. After-the-fact forms of advice (e.g., asking jurors to disregard a piece of evidence) have questionable effectiveness (e.g., Sue, Smith, & Caldwell, 1973). We also felt that expert advice should be general rather than dealing with the specifics of the case and that it should apply to all eyewitnesses (prosecution and defense) throughout the course of the trial. All of these considerations led us to treat the manipulation as an "advice" variable delivered prior to subsequent eyewitness testimony. Method One-hundred and ninety-two persons eligible for jury roles participated as subjects. Subjects were told that their role would be that of a juror evaluating the testimony of an eyewitness to a crime. Half of the subjects were first shown a videotape of a psychologist who was being questioned on a witness stand by a purported defense attorney regarding advice on eyewitness memory. (The expert advice was given by the first author of the current article.) The videotape began with a statement of the psychologist's credentials and an indication of his research activity in the eyewitness memory area. Responding to questions about the nature of eyewitness memory, the expert made two general points that set the theme for the 51/2 minutes of expert advice. The first general point was that eyewitness identification in criminal cases is different from recognizing one's friends, wherein repeated exposure and context of the encounter serve to facilitate memory to a point of near perfection. "Our research using staged crimes has shown that, depending on the conditions, anywhere from 15% to 85% of the witnesses may choose a wrong person from the lineup." The second major point focused on eyewitness confidence. It was mentioned that there was considerable evidence to show that the confidence of an eyewitness may have little or no relationship to the accuracy of the eyewitness. In response to follow-up questions by the interogator, the expert summarized this latter point, to wit "a person attempting to judge whether an eyewitness has identified an innocent suspect in a lineup or picture array should avoid placing any faith in the eyewitness' confidence.., the person should instead focus on situational factors that may have facilitated or inhibited the accuracy of the eyewitness." The two major points constituting the content of the expert advice deserve special note. Why did we decide to make these two particular points? The first point (15%-85% of eyewitnesses may choose the wrong person from a lineup) was designed to help correct the overbelief phenomenon observed in Lindsay et al. (1981). It was also hoped that by giving them a range of possible values (15%-85%) and using the phrase "depending on the conditions," the subject-jurors would focus on the witnessing conditions and show a greater tendency to modify their willingness to believe witnesses under the changing conditions. The second general point (that eyewitness confidence is an unreliable cue to an eyewitness' accuracy) was based on two con-

7 JUDGING EYEWITNESS TESTIMONY 281 siderations. First, it has been shown that eyewitnesses' confidence has an overly high impact on jurors' decisions regarding belief of the eyewitnesses (see Lindsay et al., 1981; Wells et al., 1979). When someone's judgment is heavily based on unreliable cues it leaves little room for more reliable cues to be employed. Perhaps even more damaging is the fact that heavy reliance on an unreliable cue creates an illusion that one's judgments are valid and lessens the perceived need to search for more reliable cues. We also had some empirical evidence to suggest that forcing jurors away from using the eyewitnesses' confidence as a cue to accuracy would improve on the jurors' sensitivity to witnessing conditions. Specifically, the Lindsay et al. study showed that subject-jurors were more sensitive toward witnessing conditions when the subjectjurors viewed cross-examinations of low-confidence eyewitnesses than when they viewed cross examinations of high-confidence eyewitnesses. Lindsay et al. suggested that the low-confidence witnesses induced uncertainty in the subject-jurors, leading the subject-jurors to search for other possible (more reliable) predictors of accuracy. It was hoped that telling subject-jurors to ignore witness confidence would have a similar effect. After listening to the expert advice, the subject jurors viewed a videotaped crossexamination of an eyewitness. The eyewitnesses (n = 108) were the same as those used in Lindsay, Wells, & Rumpel (1981). [See Lindsay et al. for a detailed description of the criminal event.] The three groups of witnesses differed in their likelihood of false identification with the poor, moderate, and good witnessing conditions yielding 33%, 50%, and 74% accurate identifications, respectively. We sampled 16 witnesses from each condition, half of whom had identified the thief from the photo-lineup and half of whom identified an innocent person. As in Lindsay et al. (1981) we were able to measure jurors' belief-of-witness decisions with regard to both the individual witness's accuracy and the witness's probable accuracy as a member of one of the three conditions (i.e., poor, moderate, good). Thus, the study replicates Lindsay et al. (1981) for the subject-jurors who did not receive the expert advice. Each subject-juror viewed four cross examinations of witnesses who were either accurate or inaccurate; all four witnesses came from the same condition (i.e., the poor, moderate, or good witnessing condition)? The cross examination of each eyewitness was done blind to the eyewitness's accuracy and the 15 questions included open-ended questions (e.g., "Describe what the person was wearing"), questions requiring use of specific dimensions (e.g., "How long was the person in the room?"), and questions that challenged the witness's credibility (e.g., probing possible transference from a previous encounter with the defendant), s After viewing each witness, the subject-jurors were asked to decide whether they believed the eyewitness had identified the thief or whether the eyewitness had identified an innocent person. 2The subject-jurors were told that some witnesses had seen different events. This was an attempt to keep the subject-jurors from using differences/commonalities in the witnesses' testimony to discern some "truth" about the event. An analysis reported in Lindsay et al. (1981) shows the viability of this practice in that (a) subject-jurors were no better or worse at discriminating between accurate and inaccurate eyewitnesses who were presented first versus last in the series of four and (h) the tendency of jurors to believe/disbelieve eyewitnesses was unrelated to the number of eyewitnesses viewed. across-examination scripts are available from the first author.

8 282 WELLS, LINDSAY, AND TOUS1GNANT Table 1. Percentage of Subject-Jurors Believing that the Eyewitnesses Made Accurate Identifications as Functions of the Eyewitnesses' Actual Accuracy, Witnessing Conditions, and Expert Advice a No expert advice Witnessing conditions Poor (.33) Moderate (.50) Good (.74) Overall Accurate witnesses 55% 56% 66% 59% Inaccurate witnesses 62% 58% 73% 64% Expert advice Witnessing conditions Poor (.33) Moderate (.50) Good (.74) Overall Accurate witnesses 31% 36% 56% 41% Inaccurate witnesses 42% 28% 50% 40% anumbers in parentheses represent the proportions of witnesses making accurate identifications in those witnessing conditions. Those witnesses not making an identification were not included in the figures. Results Table 1 presents the proportion of subject-jurors who believed that the witness had made an accurate identification as functions of the witnesses' actual accuracy, the witnessing conditions, and expert advice. We assigned subjects scores of 0%, 25%, 50%, 75%, or 100% for the percentage of eyewitnesses each subject believed and analyzed the data as a 2 (individual accuracy) 2 (expert advice, no expert advice) 3 (witnessing conditions) between-subjects analysis of variance. The most robust result obtained from this analysis was a main effect for expert testimony, F (1,180) = 34.18, p <.01. It is obvious from an examination of Table 1 that the expert testimony served to reduce the subject-jurors' tendencies to believe that the eyewitnesses had made accurate identifications. We also found a main effect for the witnessing conditions, F (2,180) = 8.17, p <.01. As shown in Table 1, this effect is due to the general tendency for subject-jurors to discount the testimony of the eyewitnesses who had poor or moderate witnessing conditions relative to those who had good witnessing conditions. No other effects were significant. Because there was no significant interaction effect between the expert advice manipulation and the individual accuracy of the eyewitnesses on jurors' belief, we cannot claim that the expert advice served to increase subject-jurors' abilities to discriminate between accurate and inaccurate witnesses to a given crime. The overall percentages in Table 1 show that expert advice dropped subject-jurors' belief of accurate witnesses by 18% (from 59% to 41%) and it dropped subject-jurors' belief of inaccurate witnesses by 24%. This slightly greater drop in belief of inaccurate versus ac-

9 JUDGING EYEWITNESS TESTIMONY 283 0, Zk Probable Witness Accuracy ~x [] Juror Belief Without J Expert Advice y O Juror Belief With E Q ~25 Poor Moderate Good Witnessing Conditions Fig. 1. Probabilities of witness accuracy and juror belief with and without expert advice. curate witnesses was not statistically significant, yeilding no significant improvement in subject-jurors' willingness to believe accurate versus inaccurate witnesses? There was also no significant evidence to indicate that expert advice helped the subject-jurors take better account of the witnessing conditions. Figure! shews how the expert advice and no expert advice groups performed relative to a baseline of "probable witness accuracy." Probable witness accuracy is the proportion of accurate witnesses among all witnesses who make an identification (calculated individually for each witnessing condition). Probable witness accuracy represents an actuarial value for each witnessing condition to which the juror-belief rates may be compared. If we assume that it is desirable to obtain juror-belief rates that closely correspond to probable witness accuracy rates across the witnessing conditions, then we must admit that expert advice did not produce an improvement in that regard. The average deviation between juror belief and probable witness accuracy was. 13 for the no expert advice groups and -.14 for the expert advice groups (see Figure 1). We also analyzed the effect that expert advice had on the subject-jurors' tendencies to rely on eyewitnesses' confidence in making their decisions about those eyewitnesses. To do this, we calculated a correlation between the confidence of the eyewitnesses (as measured by Likert-type scales described in Lindsay et al., 1981) and the proportion of subject-jurors who believed the eyewitnesses. The obtained correlation for subject-jurors who did not receive expert advice was +.59 (p <.05) whereas it was a mere +.16 (nonsignificant) for those receiving expert advice. Thus, we were successful in convincing the subject-jurors to reduce their reliance on eyewitness confidence. 4The reader might note that subject-jurors tended to believe inaccurate eyewitnesses slightly more often than tb.ey believed accurate eyewitnesses in some conditions. Similar results have beer~ reported in Wells et al. (1979) and Lindsay et al. (1981). We do not attribute any particular significance to this beyond its appearance as random fluctuations around chance performance.

10 284 WELLS, LINDSAY, AND TOUSIGNANT Discussion We have shown in this article that there is considerable room for improvement in assessing eyewitness testimony among triers of fact. This assumes, of course, that our subject-jurors have judgmental abilities that are roughly comparable to active jurors. We have shown that there is considerable room for learning to discriminate between accurate and inaccurate witnesses to a given crime, learning to take adequate account of witnessing conditions, learning not to heavily rely on eyewitness confidence, and learning not to overwillingly believe eyewitnesses. We have also shown how expert advice can eliminate the overbelief bias (albeit with some risk of producing "underbelief" for good witnessing conditions) and greatly reduce subject-jurors' reliance on eyewitness confidence. Had we tailored the expert advice to the specific witnessing conditions, we might also have been able to show an improvement in subject-jurors' abilities to take witnessing conditions into account. This is, of course, quite speculative. Why did we choose this general form of expert advice rather than a specific form that could be effectively tailored to the witnessing conditions? The main reason is that we hope to eventually develop a standard form of expert advice that could be routinely delivered to triers of fact. It is quite costly in terms of money and time to have specific testimony in each trial. Perhaps a scientific summary can be routinely delivered in court. Unusual cases, of course, may continue to require the use of an expert so that the expert advice can be tailored to the case at hand. We chose to deliver the expert advice information prior to the subject-jurors' viewing of the eyewitness crossexamination for much the same reason; if expert advice on eyewitness memory is to be routinely included in court cases it should be given at the beginning of the triai so that it can be maximally utilized during the cross-examination and so that it will apply equally to witnesses for the prosecution and defense. A counterargument to our choice of using a general (vs. specific) form of expert advice is that, in offering expert advice, eyewitness researchers sometimes consider the specific crime conditions and single out any factors that are of potential import. Had the staged crimes from which we obtained our eyewitnesses been an actual case and the current authors were asked to offer expert testimony, we might have "narrowed in" on the length of time that the criminal was in view and/or the wearing of the toque. Doing so might have yielded an improvement in the extent to which subjectjurors distinguished between witnessing conditions. Thus, if an expert can identify pertinent variables bearing on the likely accuracy of eyewitnesses in a given case, then expert advice on these matters might prove quite beneficial. This is purely speculative, of course, and a major problem is in defining the term "pertinent variable." As far as we are able to discern, a pertinent variable to be used in expert testimony on eyewitness memory given to triers of fact should meet three qualifications: (a) it is a variable that is known to affect eyewitness memory; (b) there is an existence of some level of that variable in the given case; and (c) the influence of that variable is not adequately appreciated by the triers of fact. Unfortunately, most of the research conducted on eyewitness testimony has focused its efforts on identifying variables that meet the first or second qualification while ignoring the third (See Loftus, 1979, Chapter 9 for an excellent exception). In other words, some of the variables we investigate may or may not already be appreciated by triers of fact--we simply

11 JUDGING EYEWITNESS TESTIMONY 285 have not examined this to its full extent. Thus, we still have some difficulty in identifying pertinent factors in a given case. We are encouraged by the results of our first attempt to experimentally assess the influence of expert advice on subject-jurors' performance in judging the validity of eyewitness testimony. At the very least our results show that people are able to use such advice to change their decision criteria even when the advice runs counter to their intuitions (as with the confidence-accuracy issue). REFERENCE NOTE!. Hastie, R. From eyewitness testimony to beyond reasonable doubt. Unpublished Northwestern University Manuscript, REFERENCES Brandon, R., & Davies, C. Wrongful impr&onment. London: Allen & Unwin, Clifford, B. R., & Bull, R. The psychology of person identification. Boston: Routledge & Kegan Paul, Deffenbacher, K. Eyewitness accuracy and confidence: Can we infer anything about relationship? This issue, Law and Human Behavior, 1980, 4, , Lindsay, R. C. L., Wells, G. L., & Rumpel, C. Can people detect eyewitness identification accuracy within and across situations? Journal of Applied Psychology. 1981, 66, Loftus, E. F. Eyewitness testimony. Cambridge, Massachusetts: Harvard University Press, Loftus, E. F. Impact of expert psychological testimony on the unreliability of eyewitness identification. Journal of Applied Psychology, 1980, 65, Munsterberg, H. On the witness stand. New York: Doubleday, Page, Sue, S., Smith, R. E., & Caldwell, C. Effects of inadmissable evidence on the decisions of simulated jurors: A moral dilemma. Journal of Applied Social Psychology, 1973, 3, Wells, G. L. Applied eyewitness testimony research: System variables and estimator variables. Journal of Personality and Social Psychology, 1978, 36, Wells, G. L., Lindsay, R. C. L., & Ferguson, T. Accuracy, confidence, and juror perceptions in eyewitness testimony. Journal of Applied Psychology, 1979, 64, Wells, G. L., & Lindsay, R. C. L. On estimating the diagnosticity of eyewitness nonidentifications. Psychological Bulletin, 1980, 87, Yarmey, A. D. The psychology of eyewitness testimony. New York: Free Press, 1979.