What is the relationship between eyewitness testimony and memory?
Knowledge of how the memory process operates has been applied to the analysis of eyewitness testimony to assess the likelihood that a witness is correct in making an identification. The task of eyewitness identification depends on the three stages of the memory process: encoding, storage, and retrieval. The last stage, retrieval, can be divided into two parts: recall and recognition. Each of these stages is subject to the influence of several factors that may contribute to error in the process.
Encoding is the stage of acquiring information. In the case of eyewitness identification, it is the sighting of a person during an event. The circumstances of the event will affect the ability of a person to encode information, including the facial appearance of another person. A short period of viewing time, poor lighting, greater distance, and an obtuse angle of view will reduce the observer’s ability to acquire information about appearance. Any distractions present will reduce the attention paid to the face of the person and reduce the facial information encoded. If there are other people present, they serve as distractions. If a weapon is present, it attracts the attention of the observer and reduces the attention to faces. This phenomenon is called the weapons effect. If the weapon is used in a threatening manner, it will be likely to attract even more attention and further reduce the encoding of facial detail. Highly salient features of the face may dominate the encoding of the face. For example, a prominent scar may attract attention and reduce the attention to other facial details. When this happens, the witness may easily mistake another person with a similar scar for the original person, even though other features are different. Only information that is encoded can be retained and retrieved later, so the encoding stage sets the limits for later identification.
Once information is encoded, it must be stored until it is retrieved for use. One is not constantly aware of the information one has; such information is held in storage until one retrieves it. The brain holds information by some electrochemical process. It is not known exactly how it works, but it is clear that the storage stage of memory is not passive and inert like a videotape. Memories can change while they are stored. The memory may change in two ways: it may fade, or it may be distorted. Information fades away over time. This effect of time on memory is one of the oldest findings in the field of psychology, documented by Hermann Ebbinghaus in 1885. His findings indicate that memory fades rapidly at first and continues to fade over time at a reducing rate. This fading could be evidenced by loss of details or a less accurate recall of details. Sometimes witnesses may still believe that they recall a face, but the memory has really changed so that their identification is inaccurate.
The other major factor affecting memory during the storage period is interference. Events that occur during the storage period may change the memory without the awareness of the witness. A witness may be exposed to information after an event and, without knowing it, incorporate that information into the memory of the event. One example of this type of effect is called unconscious transference. This occurs when a person seen in one setting is remembered as having been in another. Sometimes a witness will mistakenly identify someone seen in another setting as the one who committed a crime. The witness has, without knowing it, transferred the memory of the face of the innocent person into the crime memory.
The third stage of memory is retrieval. Witnesses may be asked to retrieve information by either recall or recognition. Giving a description of a person is an example of free recall. There are no external stimuli from which to select; witnesses simply retrieve whatever information they can. In the case of recognition, the witness is asked to identify someone from a photograph, in person, or from a group of photographs (a photo lineup) or a group of people (a live lineup). Sometimes lineups are videotaped. Recall may be distorted by suggestive questions or nonverbal cues. Elizabeth F. Loftus reported in her 1979 book Eyewitness Testimony that when people were asked, “How tall was the basketball player?” their descriptions averaged seventy-nine inches. When they were asked, “How short was the basketball player?” they estimated sixty-nine inches. This ten-inch difference was caused simply by the change in the wording of the question.
The accuracy of a witness’s recognition in lineup situations can be greatly affected by the nature of the lineup. If a witness is asked to identify a person from a single photograph or a one-person lineup, there is a possibility of error attributable to the witness’s expectation that this must be the person or the police would not produce the person. In multiple-choice lineups, the similarity of the alternative choices to the suspect is the major determinant of error. If only one or two people in the lineup are similar to the original description of a suspect, a witness really has few choices, and the result is similar to the single-choice lineup. Witnesses may sometimes select a person in a lineup who is similar to the one seen or who looks familiar for some other reason.
In some cases, the only evidence against a person accused of a crime is an identification by an eyewitness. In their 1973 book Wrongful Imprisonment: Mistaken Convictions and Their Consequences, Ruth Brandon and Christie Davies describe seventy cases in which an incorrect identification by an eyewitness led to a conviction. In 1973, after conducting his own study of the subject, New York surrogate court judge Nathan Sobel concluded that incorrect eyewitness identification led to more miscarriages of justice than all other factors combined. Because of the serious consequences of an incorrect identification and the possibility that misidentifications frequently occur, psychologists have applied their expertise in memory to the study of the factors that would affect the accuracy of eyewitness identification.
Loftus has reported a case of eyewitness testimony that illustrates one of the most important applications of the field, a criminal trial. The background to the trial began on October 12, 1977, at approximately 8:30 in the evening. Two men entered a liquor store in Watsonville, California. The first man stood directly across from a young male clerk and pointed a gun at him, demanding all the money. The second man stood four or five feet away, pointing a gun at an older clerk, who stood behind the first clerk. The first robber demanded the money from the cash register and the clerks’ wallets. As the young clerk turned to replace his wallet, he heard a shot and dove to the floor. When he looked up, the first robber was almost out the door, and the second robber stood in the doorway smiling; the older clerk lay dead on the floor. As soon as the robbers left, the young clerk hit the alarm. A security guard responded immediately, and the clerk, in a state of shock, could only say, “Two men, one with a mustache, two men, one with a mustache.”
The clerk was interviewed by police the next day, and he described one robber as a male Mexican, thirty-two to thirty-seven years old, about five feet, ten inches tall, 175 to 180 pounds, with black collar-length, unkempt hair. A composite drawing was made. During the next week, the clerk viewed two live lineups and a large set of black-and-white photographs. Two of the photographs were of a man named José Garcia. The clerk said that one of them looked similar to the robber. About a week later, the clerk viewed the set of photographs again and again said one of them was similar to the robber. Another week went by, and the clerk was shown a different set of color photographs. He picked out Garcia as “the guy; I wouldn’t forget the face.” Three days later, the clerk picked a man from a live lineup whose voice sounded like the robber. This man was an innocent police officer, so the clerk went back to the color photographs and said that Garcia was definitely the murderer.
Garcia was arrested and charged with murder and robbery. He was thirty-nine years old; he was five feet, ten inches tall, and he weighed 242 pounds. He spoke with a heavy Spanish accent and had tattoos lining both arms; his left hand was deformed from a sawblade accident.
Loftus was hired by the defense to testify about the factors that might cause the eyewitness to be inaccurate. After she was sworn in, her qualifications as an expert in eyewitness memory were presented to the court. The prosecution argued that the data from experiments only allowed general conclusions and not conclusions about the eyewitness in this case, and that experiments were not performed on real-life crimes. The judge ruled that the testimony would be heard by the jury. Through a long series of questions, the defense attorney attempted to bring before the jury the factors from the psychological research that are known to affect the ability of an eyewitness to make a correct identification. Some of the factors Loftus mentioned were the storage interval (there were several weeks between the crime and an identification), the high stress level of the witness during encoding, the possibility that the weapon used in the crime may have created a weapons focus, and the possibility that the viewing of pictures of the suspect several times before making an identification could have allowed for unconscious transference to occur.
The jury, after hearing Loftus’s expert testimony, was unable to reach a verdict. The defendant was tried again a few weeks later; the process was repeated, and again the jury could not reach a verdict, so the defendant was set free. Interviews with the jury indicated that they valued the expert testimony of Loftus in their deliberations; nine were for acquittal and three were for conviction.
In 1900, French psychologist Alfred Binet (later famous for the development of intelligence testing) argued for the creation of a practical science of testimony. German psychologist William Stern was publishing studies of eyewitness testimony as early as 1902. In 1903, Stern testified in German courts of law as an expert on eyewitness testimony. Beginning in 1909, American psychologist Guy Montrose Whipple began a four-year series of articles in Psychological Bulletin in which he translated and interpreted European work on the subject as well as presenting his own.
Although it appeared that the field was ready to develop rapidly, it did not. Probably because most psychologists of the time focused more on theoretical issues than on applied problems and because the early psychologists working on eyewitness testimony were criticized for overgeneralization, the explosion of research on eyewitness testimony did not occur until the 1970s. Ulric Neisser, in his book Cognition and Reality: Principles and Implications of Cognitive Psychology (1976) and later in Memory Observed: Remembering in Natural Contexts (1982), presented the view that the advances in understanding human memory and social perception called for a new emphasis on observations made in a natural context. The majority of the research on memory applied to eyewitness testimony has been carried out since then.
Modern research has developed a large database on variables that affect the accuracy of an eyewitness, as well as on such issues as the best way to interrogate a witness, how to construct fair lineups, and how to help witnesses remember more accurately. A major topic of the 1980s and 1990s was the usefulness and appropriateness of the testimony of psychological experts in court proceedings. Some judges do not allow psychologists to testify about eyewitness reliability; however, other judges do allow such testimony. Psychologists disagree on whether this testimony serves a good purpose. It is clear that if testimony is given, the psychologist cannot say whether a given witness is correct or not. The psychologist may provide the jury members with information that can help them to evaluate the eyewitness testimony better. There may be scientific data about the circumstances of the case being tried that jurors do not know. Telling the jurors about the data can give them a better basis for evaluating the credibility of a witness. This can lead to improvement of the judicial process by more often convicting the guilty as well as saving the innocent.
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