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Police often ask eyewitnesses to identify a suspect from a lineup or an array of photos. A lineup or photo array involves placing a suspect or a photo of a suspect among people who are not suspected of committing the crime (fillers) and asking the eyewitness to identify the perpetrator.
Misidentification by eyewitnesses has played a role in a high number of wrongful convictions and has led criminal justice experts to look more closely at the effectiveness of identifying suspects from live and photographic lineups.
Eyewitness Identification: Simultaneous vs. Sequential Lineups
Most U.S. law enforcement agencies use the simultaneous lineup, in which the eyewitness views a lineup of individuals or a photo array; that is, all individuals are viewed at the same time. However, some research has indicated that a sequential lineup, in which photographs are presented to the witness one at a time, produces fewer false identifications as well as fewer true identifications [1, .
The two types of lineups require different mental processes from the witness:
For sequential lineups, witnesses must exercise "absolute judgment," comparing each photograph or person only to their memory of what the offender looked like.
In simultaneous lineups, witnesses must use "relative judgment" to compare lineup photographs or members to each other.
Which Lineup Is Better?
So far, research that compares simultaneous and sequential lineups and the use of "blind" administrators has not been conclusive. In a blind lineup, the person who is running the lineup does not know which person the police believe is the likely suspect.
In 2006, an Illinois law enforcement project conducted a field experiment that compared double-blind sequential identification with simultaneous eyewitness identification. They found a higher rate of correct identifications in simultaneous nonblind lineups and a higher rate of false identifications in sequential double-blind lineups.
Other Variables That Can Affect Validity
Other variables that might affect the validity of either type of lineup:
- Whether the person administering the lineup is "blind" (does not know which person in the lineup is the suspect).
- The instructions given to the witness, including saying that the suspect "might or might not be present."
- Use of lineup "fillers" who do not resemble the suspect, thus making the suspect stand out. For example, the suspect has dark hair, but only one of five people in the lineup has dark hair.
- Events that occurred during the incident, such as the use of a weapon that can distract the witness from the suspect's face.
Learn more from the NIJ Journal article "Police Lineups: Making Eyewitness Identification More Reliable."
[note 1] Carlson, C. A., Gronlund, S. D., and Clark, S. E. (2008). “Lineup composition, suspect position, and the sequential lineup advantage” Journal of Experimental Psychology Applied, 14, 118-128.
[note 2] Haw, R.M. and Fisher, R.P. (2004) “Effects of Administrator-Witness Contact on Eyewitness Identification Accuracy,” Journal of Applied Psychology, 89 (6). 1106–1112.