Eyewitness Identification

Transcription

1 Law and Human Behavior, Vol. 1, No. 2, 1977 Notes and Discussions Eyewitness Identification Photographs vs. Live Models David Egan, Mark Pittner, and Alvin G. Goldstein* In a simulated crime situation, 3 groups of eyewitnesses viewed 2 target persons through a one-way mirror and were tested for accuracy of identification after delay periods of 2, 21, or 56 days. Subjects made identifications from either a live "show-up" or by looking at photographs. In both methods of testing only 1 of the 2 targets was actually present in the 5-man array. Results indicated that delay affects number of false alarms, test method affects number of hits. Photographs produced less accurate performance than live show-up. More than 60% of the subjects erroneously selected one of the 4 distractor persons, a finding relevant to the use of eyewitness identification in criminal investigations. Only 28% of the subjects made no errors of identification. INTRODUCTION In certain kinds of criminal investigations, the validity of eyewitnesses identification of the suspect poses recurrent and particularly perplexing problems. Even though identification of criminals by witnesses is an important and indispensible method available to criminal investigators, it is a method with inherent subtle dangers. Although the absolute size of the problem remains unknown (and perhaps unknowable) there is ample evidence to justify the belief that many people have been erroneously convicted of crimes solely on the strength of the testimony of eyewitnesses (Wall, 1965; Evans, 1976; Goldstein, 1977; People vs. Anderson, 1973; Brandon and Davies, 1973). These errors are appalling primarily because of the human suffering they cause; they are in addition critically important because our system of law enforcement is in principle dedicated to fairness, to the concept that it is better to acquit a guilty person than to convict an innocent one. In spite of these considerations, with *The first and second authors, listed alphabetically, shared equal responsibility for this research. Reprint requests should be addressed to: Alvin G. Goldstein, Psychology Department, McAlester Hall, University of Missouri, Columbia, Missouri, This journal is copyrighted by Plenum. Each article is available for $7.50 from Plenum Publishing Corporation, 227 West 17th Street, New York, N.Y

2 200 EGAN ET AL. few exceptions (e.g., Buckhout, 1974; Doob & Kirshenbaum, 1973), relatively little systematic research has been done to define the factors that affect accuracy of identification in lineups or other methods of personal identification used by criminal investigators (Levine and Tapp, 1973, p. 1130). This experiment attempted to explore several questions related to eyewitness veridicality. Untested opinions recommending the best methods of conducting lineups are relatively common and may be influential. For example, Justice Traynor of the California Supreme Court, stated in a case review that "Identification from a still photograph is substantially less reliable than identification of an individual seen in person" (People vs. Gould, 1960). And again Wall states that "a corporeal identification, if properly obtained, is more reliable than a photographic one" (1965). Opinions such as these are unsupported by evidence, and if taken seriously could result in modifications of procedures associated with eyewitness identification that might further reduce the reliability of eyewitness testimony. One purpose of the present study was to determine whether the corporeal or photographic method of identification is more accurate. Also studied was the effect of the length of the interval between the witnessing of the "crime" (study phase period) and the lineup or mug shot inspection (test phase period). Investigations of recognition memory for several kinds of pictorial stimuli suggests that the length of the study-test interval affects accuracy of performance (e.g., Nickerson, 1968), but this relationship was not confirmed in other studies (Clark, 1965; Goldstein and Chance, 1970). Sex differences in face recognition have been demonstrated (Goldstein and Chance, 1970; Lane, 1972; Laughery, Alexander and Lane, 1971), but the effect may be weak (Laughery, 1972; Yin, 1969). Even the kind of photograph used (color v. black and white) in the mug shot inspection may affect recognition performance (Laughery, 1972; Sussman, Sugarman, and Zavala, 1972), but the conclusion is not firm (Laughery et al., 1971; Laughery, 1972; Pavio, Rogers, and Smythe, 1968). It is reasonable to assume that police may be much more likely to arrest or at least temporarily detain a person if the eyewitness is behaviorally confident of his identification. That is, subjective confidence is an important variable to consider in criminal investigations. Several studies have measured confidence using scales designed for this purpose (Laughery et al., 1971; Laughery, 1972; Sussman and Sugarman, 1972) and the present investigation also incorporates a subjective confidence measure. In this study a 2 3 factorial design with two methods of identification in the test phase (photographic v. corporeal), and three intervals between study and test phase (2, 21, and 56 days) was employed. The procedure was designed to resemble the task confronting an eyewitness attempting to identify a culprit following a crime. METHOD Subjects. Subjects were 86 (50 men, 36 women) undergraduate students enrolled in general psychology courses who received extra course credit for participating. Procedure (Study Trials). Subjects were brought into a small conference room in

3 EYEWITNESS IDENTIFICATION 201 groups of from five to ten, and were seated directly in front of a large one-way mirror. They were informed about the general nature of the study, and were instructed to roleplay an eyewitness to a crime. The role-play instructions portrayed the subjects as accidental witnesses to a crime in which two men robbed and shot a store proprietor while the witnesses remained hidden from view. Subjects were told to imagine that each was the sole witness and that their identification of the criminal would be crucial. Subjects viewed two confederates, who were the "criminals" (hereinafter called "targets") in the hypothetical robbery. The two targets entered the room on the other side of the glass partition, stopped in front of the mirror~ then left the room. Both targets were dressed alike in blue jeans and white T-shirts, and were visible to the subjects for approximately 15 seconds. Continuing the role-play instructions, each subject was asked to imagine that the police soon arrived, at which time they informed the subject that few clues existed, and that he/she would be called upon at some future date to identify the target in a lineup. Test Trials. Independent groups of subjects were tested 2 days (N = 33), 21 days (N = 24), or 56 clays (N = 29) following the study trial. Small groups of subjects were tested in the same room where the study trials took place earlier. They were asked again to role-play an eyewitness and to imagine that the police had summoned them to view a lineup (or to view mug-shot photographs). They were reminded that the only evidence implicating the robbers was eyewitness testimony, and that their testimony should be carefully considered because their identifications could convict the guilty or the innocent. Before viewing the lineup, one-half of the subjects in each condition were asked the following question: "How sure are you that the identifications you will make will be accurate?" Responses to this question were made on a 7-point interval scale ranging from extremely certain (7) to extremely uncertain (1). The remaining subjects in each condition were asked this question after viewing the lineup. Two kinds of recognition tests were used, an actual lineup (corporeal), and photographs (mug shots). Subjects saw one or the other, not both. Two photographs (one full length, head on, and one full face) of each of 5 young men were used. All were dressed alike in T-shirts and jeans; pictures were black and white, 3.5 X 5 in. taken about 4 months before the experiment. Of the 5 men, only one was a target person; the remaining 4 were distractors. Subjects were given individual packets containing the series of 10 photographs. In the corporeal condition, these 5 men appeared in a line-up in front of the subjects, dressed as they were in the photographs. In both conditions, the target person always appeared in either position 2 or 5 (counting from the subject's left), and the position of the four distractor persons was randomly determined for each presentation. Six men (college age) served as confederates; two were always target individuals, and four were distractors. Although only one of the two targets appeared in the five-man lineup, one-half of the subjects viewed one target, the remaining subjects viewed the second target individual. Confederates were selected to look alike; all were similar in height, weight, and hair color (light). Subjects in both conditions were required to make two decisions for each of the 5 persons: (1) a yes-no response to the question, "Do you recognize him as one of the criminals?" and (2) "How certain (certain, moderately certain, uncertain) are you that your response is correct?"

4 202 EGAN ET AL, Those subjects who inquired whether both targets would be in the five-man lineups were given the following reply: "You were the only eyewitness and therefore you are the only person who knows." Subjects were advised to look carefully at all 5 people before making their judgments; decision time was unlimited. Individual response sheets were used by the subjects to record their choices and their judgments. RESULTS Scoring. A composite scale of accuracy was used to assign one score to each subject's overall performance. A hit and miss denotes a yes and no, respectively, to the target person (i.e., in a criminal investigation a "hit" means the eyewitness correctly identified the culprit, and a "miss" means the culprit was in the lineup, but he was not identified). A false alarm (FA) refers to a yes response to one or more distractors (i.e., the eyewitness selects the wrong man as the criminal); a correction rejection (CR) refers to a no response to the distractors. Thus, a score of 5 reflects a hit without an FA, 4 indicates a miss without an FA, 3 a hit plus one FA, 2 a miss plus one FA, and finally 1 indicates two FA responses. Overall Performance. The hit rate across all conditions was 91%, with 78 of the 86 subjects correctly identifying the target suspect. However, the false alarm rate was a surprisingly high 67%, with 58 of the 86 subjects making at least one false alarm. Only 28% of the subjects made no errors of identification. For each dependent measure discussed below, except where indicated, the results of a 2 (method) X 2 (sex) X 3 (delay) analysis of variance will be reported. The position of the target person (second or fifth) had no reliable effect on responses and will be omitted from all subsequent analyses. Hit Rate. Analysis of simple hit rate indicates that the method of presenting the recognition stimuli was the only variable that significantly affected subjects' recognition of the target stimuli. With hits assigned 1, and misses assigned 0, subjects who viewed the corporeal lineups in the test phase performed significantly better (X =.975) than those who viewed the photographic lineups (~" =.847; F (1,71) = 4.31, p <.05). In other words, 98% of the subjects who viewed the corporeal lineup, and 85% of the subjects who viewed the photographs successfully identified the target; this difference in hit rate did not interact with either delay interval or sex of subject variables. False Alarms. Analysis of incorrect responses to distractor stimuli disclosed that only the length of delay between study and test trials approached significance IF (2,71) = 2.47, p <.10]. The number of FAs increased as the delay interval increased, with 48% of the 2-day, 62% of the 21-day, and 93% of the 56-day subjects making FAs. Accuracy. Analysis of scores derived from the 5-point accuracy scale (described above) disclosed a marginally significant IF (1,71) = 2.45, p <.10] decrease in accuracy as a function of increasing delay between study and test trials. The mean accuracy scores for the 2-day, 21-day, and 56-day subjects were 3.9, 3.5, and 3.1 respectively. This decrease in accuracy over time is supported by an analysis of the data for the 28% (24 of 86) of the subjects who were totally accurate in their identifications, that is, they correctly identified the target and made no FAs. The distribution of these subjects' scores was significantly related to length of delay (X 2 = 11.46, p <.05); 45%

5 EYEWITNESS IDENTIFICATION 203 of 2-day subjects made perfect scores, whereas 29% of 21-day subjects and only 7% of the 56-day subjects were able to recognize the one target person and avoid misidentifying the distractor persons. Subjective Accuracy Estimation. Subjects who were asked just before the recognition test to estimate (on a 7-point rating scale) their self-confidence in making an accurate identification were significantly less confident (-~B = 4.38) than subjects who rated themselves after the recognition test (-~A = 5.14; t (86) = 2.49, p <.01)~ It is reasonable to expect differences in confidence judgments from subjects who made errors and those who did not. Acting on that expectation, data of subjects who committed at least one error in identification were analyzed. The before subjects rated themselves as less confident (XB = 4.32) than the after subjects (-Y(A = 4.84; t (62) = 1.46, p <.05). 1 Additional analysis along these lines reveals that often subjects may "know" the difference between a hit and an FA even as they make the wrong choice. Confidence ratings of 54 subjects who identified the target and also erroneously selected one of the distractors were analyzed. Hits were reliably associated with expressions of greater confidence (.Y( = 1.78 on a scale from 1 to 3) than FAs (X = 1.04, t (54) = 7.71, p <.01). DISCUSSION Several results allow clear conclusions to be drawn, conclusions which most likely bear upon the situation one would encounter in real life. The mean hit rate was relatively high (91%) compared to hit rates reported by several other investigators (e.g., Laughery, 1971; Ellis, 1975), but only 28% of the subjects identified the correct person and did not misidentify a second individual. * The high hit rate is not anomalous when one recalls that only two targets were viewed for a fairly long observation period (15 sec) by subjects prepared to study the targets, and only 5 people (instead of the dozens typically used in recognition memory studies) were in the test array? In contrast to the degree of accuracy implied by these data, the incidence of FAs suggests that performance in this situation -- and presumably in real life w is complexly determined. It is not simply whether the observer is able to recognize the person seen before; other conditions surrounding the task have important influences on performance. Correct identification in criminal investigations is not controlled by a simple all-or-none memory function; it is not merely a case of a witness recognizing or failing to recognize a face seen at an earlier time. We have sampled only a few of the large number of factors that probably affect the accuracy of witnesses' final judgments. One-tail t tests were computed for both these analyses. In an earlier investigation (Adkins, C., Egan, D., Peterson, L., and Pittner, M., 1974) "before" subjects were found to be reliably less confident than "after" when data from all subjects were considered [XB = 5.57 and XA = 7,13; t (108) = 3.69,p <.01] and when data from only subjects who made at least one error (-~B = 5.00 andxa = 6.33; t (50) = 2.36, p <.05) were considered. ~These subjects were approximately equally distributed between the live and picture conditions. SFaces were not the sole cues for identification in this experiment. Both photographs and live show-up included views of the target's body.

6 204 EGAN ET AL. Recognizing a briefly seen unfamiliar face or person is, under normal circumstances, a highly skilled behavior with relatively low but still appreciable error rates. If the face is present in the test session (or lineup) almost all people in laboratory tests will correctly identify the target. But there is ample evidence here to infer that if the real culprit is not in the lineup, or in the mug shot display, someone may well be erroneously identified in his place. Even though recognition memory performance for the target person was very near perfect, the number of FAs committed by a relatively large number of subjects points to an underlying process characterized by a fuzzy and unstable "trace." Under these circumstances recognition memory behavior may not be a "fail safe" process. On the contrary, 67% of the subjects selected two men when they could just as easily have refrained from making the second erroneous choice. This behavior would be disturbing in almost any context, but it is even more so because subjects are aware at a vague but still measurable level that they are more uncertain of their choices when they are wrong than when they are correct. These data are additionally upsetting, for they suggest that large numbers of FAs are elicited even in a social context that did not pressure the subject to "find two criminals." What can we expect from an eye witness in a police station where the demand characteristics of the situation are far more likely to cause him or her to "find" the culprit? We suggest that our data may offer an explanation for the ever-present and never quite eradicated incidence of cases of mistaken identity, where innocent people are accused and convicted on the basis of eyewitness evidence alone. Not unexpectedly, the results of this investigation suggest that, as the time interval between the crime and the final identification procedure increases, error probability also increases. We found that even though the hit rate remained reliably high across the 56 days of the experiment, FAs increased from 48% to 93% over the same period of time. This finding, although just shy of the.05 level of confidence, is large enough to seriously call into question the judicial system's implicit assumption that eyewitnesses have perfect memories unaffected by the passage of time, and to reaffirm the obvious fact that real people make errors and the errors are more frequent with increased lapses of time. Analysis of the 5-point accuracy scale data offers further support for this conclusion. This scale, which includes hits, misses, FAs, and CRs, offers a shorthand characterization of the adequacy of subjects' performances. It is especially relevant to criminal investigations since scores at the high (5) end reflect recognition memory performance that would be associated with a low probability of any kind of error. In contrast, scores from the middle and low end of the scale reflect judgments that would normally be associated with intolerable levels of probable error. Our results suggest that with increased delay accuracy deteriorated. This effect was especially notable in the chi-square analysis of the dwindling number of subjects who made no errors on the second (45%), twenty-first (29%), and fifty-sixth day (7%) after the study session. Both common sense and the opinions of many judicial authorities (e.g., People v. Gould, 1960; Wall, 1965) were vindicated by the hit-rate data; live targets were more reliably identified than photographs of targets (97% vs 85%), and this difference in performance held up for both men and women at all delay intervals. Clearly, this finding suggests that the use of pictures instead of live individuals in identification

7 EYEWITNESS IDENTIFICATION 205 procedures increases the risk of error. The risk may be greater than implied by the 12% difference in performance between the two test methods. This is so because in criminal investigations mug-book identification typically precedes live identification, and, as we have seen, a witness's level of confidence regarding the accuracy of his performance may increase after he has actually committed an error. This fact would not by itself lead to an increase in the number of errors committed by witnesses, but it would certainly decrease the probability that a witness would change his or her mind after making an erroneous identification. Furthermore, witnesses typically view many photographs, and earlier research indicates that the probability of correctly identifying the target is inversely related to the number of distractors viewed before the target is seen (Alexander, 1972; Lane, 1972; Laughery, 1972). The photographic identification procedure is an extremely important, perhaps indispensible, technique in criminal investigations, but it is a procedure that bas to be employed with extreme caution because its use can set the stage for a series of interlocking errors beginning with a witness who is "positive" that the face in the mug book is the culprit followed by another "positive" identification of a live person. Since the first judgment has some error associated with it, the second judgment may well be nothing more than a confirmation of the mug book identification, not of the actual criminal. REFERENCES Adkins, C., Egan, D., Peterson, L., and Pittner, M. The effects of exposure time, delay, and method of presentation on the recognition of human faces. Unpublished manuscript, Alexander, J.F. Search factors influencing personal appearance identification. In A. Zavala & J.J. Paley (Eds.), Personal appearance identification. Springfield, Illinois: Charles C. Thomas, Brandon, R., & Davies, C. Wrongful imprisonment. Hamden, Connecticut: Shoestring Press, Buckhout, R. Eyewitness testimony. Scientific American, 1974, 231, Clark, H. Recognition memory for random shapes as a function of complexity, association value, and delay. Journal of Experimental Psychology, 1965, 69, Doob, A.N., & Kirshenbaum, H.M. Bias in police lineups -- partial remembering. Journal of Police Science and Administration, 1973, 1, Ellis, H.D. Recognizing faces. British Journal of Psychology, 1975, 66, Evans, P. Britain in brief. APA Monitor, 1976, 7, 6. Goldstein, A.G. The fallibility of the eyewitness: Psychological evidence. In B.D. Sales (Ed)., Psychology in the legal process. New York: Spectrum Publications, Goldstein, A.G., and Chance, J. Visual recognition memory for complex configurations. Perception and Psychophysics, 1970, 9, Lane, A.B. Effects of pose position on identification. In A: Zavala and J.J. Paley (Eds.), Personal appearance identification. Springfield, Illinois: Charles C. Thomas, Laughery, K.R. Photograph type and cross-racial factors in facial identification. In A. Zavala & J.J. Paley (Eds.), Personal appearance identification. Springfield, Illinois: Charles C. Thomas, Laughery, K.R., Alexander, J.F., & Lane, A. B. Recognition of human faces: Effects of target exposure time, target position and type of photograph. Journal of Applied Psychology, 197l, 55, Levine, F.J., & Tapp, J.L. The psychology of criminal identification: The gap from Wade to Kirby. University of Pennsylvania Law Review, 1973, 121, Nickerson, R. A note on long-term recognition memory for pictorial material. Psychonomic Science, 1968, I1, 58. Pavio, A., Rogers, T., & Smyth, P. Why are pictures easier to recall than words? Psychonomic Science, 1968, 11, People vs. Anderson, 205 North Western Reporter, 2d 461 (1973).

8 206 EGAN ET AL. People vs. Gould, 54 Cal. 2d 621, 7 Cal. Reporter 273,278,354 P. 2d 865,870 (1960). Sussman, E.D., & Sugarman, R.C. The effect of certain distractors on identification by witnesses. In A. Zavala & J.J. Paley (Eds.), Personal appearance identification. Springfield, Illinois: Charles C. Thomas, Sussman, E.D., Sugarman, R.C., &-Zavala, A. A comparison of three media used in identification procedures. In A. Zavala & J.J. Paley (Eds.), Personal appearance identification. Springfield, Illinois: Charles C. Thomas, Wall, P. Eyewitness Identification in Criminal Cases. Springfield, Illinois: Charles C. Thomas, Yin, R. Looking at upside-down faces. Journal of Experimental Psychology, 1969, 81,