Simultaneous and sequential presentation refers to two styles of presenting a police lineup to witnesses of a crime. Research shows that patterns in identification decisions differ between these presentation styles. This entry reviews the components of each presentation method and the advantages and disadvantages of their use and mentions some unresolved issues.
Some crimes involve perpetrators who are strangers to the victims and to eyewitnesses. When a suspect is identified by a police investigator, the investigator may ask the witness to view that suspect in a lineup or photo array containing the suspect and others who are known to be innocent (referred to as fillers, foils, or distracters). Four outcomes are possible: The witness can select the suspect, select a filler, respond that the suspect is not in the lineup, or give a response of “don’t know.” Obviously, the accuracy of selections and rejections of suspects depends on whether the suspect is actually guilty.
Simultaneous presentation of a lineup involves showing a witness all the members of a lineup at once. Thus, witnesses decide whether the criminal is present while looking at the entire lineup. Traditionally, police investigators have used simultaneous lineup presentation.
Research suggests that simultaneous presentation encourages witnesses to choose the person in the lineup who looks most like the perpetrator. This comparative approach is referred to as a “relative judgment strategy.” If the guilty person is in the lineup, using relative judgments should lead to correct identification. However, evidence can lead police officers to suspect an innocent person. In some portion of these occasions, the innocent suspect will look more like the criminal than other lineup members. This would make it likely that the innocent suspect would be chosen by witnesses using the relative judgment strategy. As evidence mounted that many innocent people were selected from lineups, the use of a relative judgment strategy was posited as a possible explanation for the frequency of such errors. One way to increase the accuracy of eyewitness decisions was to develop a lineup technique that decreased the likelihood that witnesses would use a relative judgment strategy when viewing the lineup.
Sequential presentation of lineups was proposed as a means to elicit fewer false selections than simultaneous lineups by reducing reliance on relative judgments. In its original formulation, sequential presentation involved the following five principles. First, each lineup member is individually shown to the witness. This discourages comparisons among lineup members and encourages witnesses to compare each lineup member only with his or her memory for the criminal (often referred to as an absolute judgment). Second, lineup members are shown only once, discouraging comparisons between lineup members because individual lineup members cannot be viewed repeatedly. Third, witnesses are unaware of how many lineup members they will be shown. This is designed to prevent wit-nesses from feeling pressure to choose as they get closer to the end of the lineup. Fourth, witnesses are not permitted to change a decision once it has been made. Finally, the person showing the lineup to the witness should not know which lineup member is the suspect (double-blind testing), so that witnesses are not prompted or cued (intentionally or otherwise) to choose suspects for reasons other than recognizing them.
There is no doubt that the sequential lineup achieved its primary purpose. Sequential lineups consistently led to fewer false selections than simultaneous lineups. The effect of using sequential lineups on correct selections is less clear. Early studies reported little or no decline in correct selection rates. The pattern of large decreases in false-positive choices combined with relatively small losses of correct selections in comparison with simultaneous lineups has been termed the “sequential superiority effect.” Later research produced mixed results with regard to correct selections, and meta-analyses support the conclusion that a real but smaller decrease occurs for correct selections than for false selections.
Several issues remain to be resolved concerning simultaneous versus sequential lineup presentation. The reason for the difference in correct selection rates has been attributed to a criterion shift, a multiple-choice selection strategy (relative judgment), and guessing. Both in the laboratory and in the police station, there is variance in the sequential procedure. Not all features of the sequential lineup have been used in every study or in the field. Sometimes witnesses are permitted to see all lineup members before making a decision. For example, in England, the mandated procedure for the police using a sequential lineup is to have witnesses go through the lineup at least twice before making their decisions known. Not all studies mask the size of the lineup. Practices vary in terms of whether the lineup is terminated after a selection is made. To date, there are insufficient data to determine the degree to which these methodological issues are crucial to the size or existence of the full “sequential superiority effect.” What is clear is that simultaneous presentation, the traditional technique for presenting a police lineup, is not ideal because of high false-positive selection rates. Sequential lineups lead to dramatically fewer false selections than simultaneous lineups but also lead to somewhat fewer correct selections.
- Lindsay, R. C. L., & Wells, G. L. (1985). Improving eyewitness identification from lineups: Simultaneous versus sequential lineup presentations. Journal of Applied Psychology, 70, 556-564.
- Steblay, N., Dysart, J., Fulero, S., & Lindsay, R. C. L. (2001). Eyewitness accuracy rates in sequential and simultaneous lineup presentations: A meta-analytic comparison. Law and Human Behavior, 25, 459-173.