Landmark study gives law enforcement better tools to reduce errors
The September execution of Georgia inmate Troy Davis compels us to consider the unthinkable: whether a state's criminal justice system has put to death a person innocent of the crimes for which they were convicted. The execution, based almost exclusively on eyewitness identification evidence, came the same week the American Judicature Society (AJS) released a national field study on eyewitness identification that has major implications for reducing wrongful convictions in the United States.
The two events reinforce the importance of employing the most reliable tools available to us in the administration of justice. A Test of the Simultaneous vs. Sequential Lineup Methods: An Initial Report of the AJS National Eyewitness Identification Field Studies, describes eyewitness identification procedures that can counter a leading cause of wrongful convictions nationwide: the misidentification of suspects in police lineups.
Lineups are an age-old tool used by law enforcement to convict the guilty and exonerate the innocent. The technique is simple and straightforward; the eyewitness views a lineup in which the suspect is embedded among fillers. The presumption is that if the suspect is guilty, the witness will identify the suspect - whereas if the suspect is innocent the witness will identify no one.
However, eyewitness identification evidence is not always reliable. DNA-based exonerations of the innocent show that 75% are cases involving mistaken eyewitness identifications. Psychologists have been conducting laboratory studies on this problem for more than 30 years, and have proposed a number of possible reforms to the procedures used in conducting lineups.
AJS1 in collaboration with the Police Foundation, the Innocence Project, and the Center for ProblemOriented Policing, implemented this national field study at four law enforcement agencies to determine which lineup method - sequential (witness views lineup members one at a time) or simultaneous (all lineup members are presented as a group) - is more accurate. The study was designed to correct some of the problems in a 2006 Illinois study that later was found to have used flawed methodology. Unlike that study, which attempted to compare double-blind sequential lineups to non-blind simultaneous lineups, all of the lineups in the AJS study were conducted double-blind, meaning the officer administering the lineup did not know the suspect's identity, and the witness was told that the officer did not know. Additionally, the witnesses or victims in the AJS study did not know they were part of an actual study and were randomly assigned to either a simultaneous or sequential procedure.
Iowa State University Professor of Psychology Dr. Gary L. Wells, the study's lead scientist and director of social sciences for the (AJS) Center for Forensic Science and Public Policy, established long ago that eyewitness identification of suspects in police lineups is much more prone to error than people think. Part of the problem stems from the standard procedure in which lineup members are presented as a group. When lineup members are presented as a group, witnesses tend to compare the members to each other, to figure out who looks most like the perpetrator and then identify that person. But, if the actual perpetrator is not in the lineup, there remains someone who looks more like the perpetrator than the others, and that person is at risk of being mistakenly identified. …