Eyewitness Identification: Psychological Aspects

Eyewitness researchers have called the usual procedure for lineups the simultaneous procedure because all members of the lineup are presented at one time. Simultaneous procedures tend to encourage eyewitnesses to compare one lineup member to another lineup member and hone in on the one who looks most like the perpetrator.

An alternative procedure, based on sequential presentation methods, was developed and tested in 1985 (Lindsay and Wells). The sequential procedure presents the eyewitness with one lineup member at a time and requires the eyewitness to make a yes/no decision on each lineup member before viewing the next lineup member. The sequential procedure prevents the eyewitness from merely making a decision as to which lineup member looks most like the perpetrator. Although eyewitnesses can compare the person being viewed at any given time to ones viewed previously, they cannot be sure what the next lineup member will look like. Hence, eyewitnesses must largely abandon the strategy of simply picking the person who looks most like the perpetrator and instead compare each lineup member to their memory of the perpetrator. The sequential procedure has proven itself superior to the simultaneous procedure. When the actual perpetrator is in the lineup, the chances of selecting that person are nearly identical with the simultaneous and sequential procedures. When the actual perpetrator is not in the lineup, on the other hand, the simultaneous procedure produces a considerably higher rate of mistaken identifications than does the sequential procedure. As with proper instructions and proper selection of fillers, the sequential procedure results in a net improvement in eyewitness identification performance. This result is one of the most replicated findings in the eyewitness identification literature and appears to be quite robust.

A major concern of eyewitness researchers has been the behavior of the lineup administrator (Wells et al., 1998). This concern has been especially stressed with regard to photographic lineups, which constitute the majority of initial identifications of criminal suspects. In the United States, courts have held that the suspect has no right to have counsel present for photographic identification procedures. Accordingly, photographic identification procedures are almost always administered by the case detectives with no other observers present. The case detectives are well aware of which lineup member is the suspect because they are the ones who developed the suspect in the first place and put the lineup together. The experimenter expectancy effect, well known in psychology, occurs when the person (e.g., an experimenter) is aware of the desired response and unintentionally (even without awareness) influences the subject to give the desired response. In a lineup situation, verbal and non-verbal interactions between the witness and the investigator should be of great concern because the eyewitness is supposed to use only his or her memory, free from external influences, to make the decision. Recent research indicates that the knowledge of the person administering the lineup can influence the eyewitness to pick the wrong person when the lineup administrator has the wrong person as the suspect (Phillips, McAuliff, Kovera, and Cutler). For this reason, eyewitness researchers have argued strongly that the person who administers the lineup should not be aware of which person in the lineup is the suspect. This solution is known in science as double-blind testing and researchers have been trying to get the criminal justice system to adopt this simple but effective technique for improving the integrity of the identification process.