Eyewitness misidentification is the single greatest cause of wrongful convictions nationwide, playing a role in more than 75% of convictions overturned through DNA testing.
While eyewitness testimony can be persuasive evidence before a judge or jury, 30 years of strong social science research has proven that eyewitness identification is often unreliable. Research shows that the human mind is not like a tape recorder; we neither record events exactly as we see them, nor recall them like a tape that has been rewound. Instead, witness memory is like any other evidence at a crime scene; it must be preserved carefully and retrieved methodically, or it can be contaminated.
When witnesses get it wrong
In case after case, DNA has proven what scientists already know — that eyewitness identification is frequently inaccurate. In the wrongful convictions caused by eyewitness misidentification, the circumstances varied, but judges and juries all relied on testimony that could have been more accurate if reforms proven by science had been implemented. The Innocence Project has worked on cases in which:
• A witness made an identification in a “show-up” procedure from the back of a police car hundreds of feet away from the suspect in a poorly lit parking lot in the middle of the night.
• A witness in a rape case was shown a photo array where only one photo of the person police suspected was the perpetrator was marked with an “R.”
• Witnesses substantially changed their description of a perpetrator (including key information such as height, weight and presence of facial hair) after they learned more about a particular suspect.
• Witnesses only made an identification after multiple photo arrays or lineups — and then made hesitant identifications (saying they “thought” the person “might be” the perpetrator, for example), but at trial the jury was told the witnesses did not waver in identifying the suspect.
Variables impacting accuracy of identifications
Leading social science researchers identify two main categories of variables affecting eyewitness identification: estimator variables and system variables.
Estimator variables are those that cannot be controlled by the criminal justice system. They include simple factors like the lighting when the crime took place or the distance from which the witness saw the perpetrator. Estimator variables also include more complex factors, including race (identifications have proven to be less accurate when witnesses are identifying perpetrators of a different race), the presence of a weapon during a crime and the degree of stress or trauma a witness experienced while seeing the perpetrator.
System variables are those that the criminal justice system can and should control. They include all of the ways that law enforcement agencies retrieve and record witness memory, such as lineups, photo arrays and other identification procedures. System variables that substantially impact the accuracy of identifications include the type of lineup used, the selection of “fillers” (or members of a lineup or photo array who are not the actual suspect), blind administration, instructions to witnesses before identification procedures, administration of lineups or photo arrays, and communication with witnesses after they make an identification.