Comparing 48-Person Lineups with a 96-Person Lineup

There is insufficient data on the effect of lineup size on identifications in large lineups. This study therefore compared 48-person lineups, a size used often in large lineup experiments, with a lineup double the size, 96. At least one hour after viewing a two-minute video featuring the target, other people and other objects, 52 participants viewed 48-person lineups (four screens of 12) or a 96-person lineup (eight screens of 12). No difference was found in the rate of identifications between the two lineup sizes. The conclusion is that the larger lineup is superior due to the smaller chance of mistakenly choosing an innocent suspect.


Introduction
A fair lineup is one in which each of the foils and the innocent or guilty suspect have an equal chance of being chosen by people who have never seen the suspect ["mock witnesses", Doob & Kirshenbaum [1], who have been given a description of the target].
The lineup is the safest eyewitness identification procedure, because the foils provide some protection to an innocent suspect.
However, it is far from perfect. There is ample evidence that witnesses often choose someone who is not the culprit Conners et al. [2]; Scheck, Neufeld, & Dwyer [3], Valentine, Pickering & Darling [4]; Wells et al. [5]. When they choose, and that person is not the suspect but a known innocent, the police know that they have erred.
However, in a fair simultaneous lineup by chance these witnesses who choose "identify" a suspect who is innocent 1/N times, where N is the lineup size. With the common American lineup size of six, this will happen 1/6=0.167, or almost 17% of the time. There is a second error that witnesses often make which goes undetected by the police: witnesses fail to identify guilty suspects Levi [6]. While a number of innovative lineup procedures have been developed to reduce mistaken identifications Levi [7], Levi [8], Pryke et al. [9], there have been few procedures available to increase correct ones that do not simultaneously increase mistaken ones. The danger of mistaken identifications has been considered so great that in the wake of research showing that we can reduce them if we warn witnesses that the culprit may not be in the lineup Malpass & Devine [10] the warning has been included in one of four recommendations of a White Paper of the American Psychological Association Wells et al. [5] to improve lineup identification evidence.
Yet experimental witnesses choose someone 57% of the time when the "culprit" is absent when shown a simultaneous lineup Steblay, Dysart, and Wells [11], even with the warning. In a fair lineup, the innocent suspect will be chosen in the traditional sixperson American lineup 57/6 = 9.5% of the time. This seems quite a large danger for an innocent suspect. Lindsay and Wells introduced sequential lineups. Their data, and a meta-analysis Steblay et al. [11], indicate that its chief advantage is in reduced mistaken identifications. Only 36% mistaken choices in culprit-absent lineups are made. Thus, in the traditional six-person American lineup the innocent suspect will be chosen 36/6 = 6% of the time.

This remains too large a large danger for an innocent suspect
Dupuis & Lindsay [12]. Levi and Lindsay [13] proposed exploring large lineups. They theorized that enlarging lineups could reduce false recognitions, if the rate by which witnesses chose someone in target-absent lineups increased less than the increased lineup size.
Thus, if a 40-person lineup had the same rate of mistaken choices as the six-person lineup, the number of false identifications would be 57/40 = 1.04%. This would clearly be a tremendous improvement.
Levi [8] has been experimenting with very large lineups, the largest Levi has conducted a number of experiments using a twominute video as the eyewitness event, and a 48-person lineup Levi [14][15][16][17][18][19][20], Levi & Menashe [21]. The rate of identifications of the target in target-present lineups was usually about 33%. There is some doubt as to whether this rate will generalize to larger lineups.
In Levi's original experiments Levi [8], the eyewitness event was very difficult. A student accompanied Levi when he recruited his participants. The student found a mutually acceptable time for the experiment and asked for the first name and phone number of the participant. He was clearly viewed by the participants are merely performing a clerical function for Levi, and thus minimal attention was given to him. When Levi arrived back and informed the participant that he was conducting a lineup and the person that they were to identify was the student, they found the task very difficult, and rates of identification very low. The fact that no difference was found in the rate of identification as the lineup grew in size The video and the lineup were shown on a tablet.
The lineups: Photos for the lineups were chosen from Levi [8]. All lineup members were young adult males who had dark and short hair, dark eyes, no beard or moustache, and were of medium build. The target also fit this description. The twelve faces of each screen were organized in two lines of six. The target was placed in the lower line one before the end from the right.

Procedure:
Participants Were Told: I am now going to conduct a lineup.
The person you are to identify is the man who walked between the rooms. He may not be in the lineup. I will show you a 4 screens (for 48-person lineups, or 8 for the 96-person lineup), each containing twelve photos. All the photos are of different people. You may view the screens as many times are you wish before coming to a decision, whether the person is in the lineup, and if so who he is".
Each participant was then shown the lineup.

Results and Discussion
The difference in number of identifications was tested using the test for the difference between two proportions Walpole [22]: z = 0.074, not even approaching significance. Since there is no difference in identifications between the lineups, the 96-person lineup is superior ( Table 1). The chance of mistakenly identifying an innocent suspect in the 96-person lineup is half that of the 48-person lineup, assuming that there is no greater likelihood of mistakenly choosing someone in the larger lineup. Both the results in Levi [8] and the failure to find any difference in the number of foil choices between the two lineups supports this assumption.