The outcome of a criminal case often depends on eyewitness identification of the defendant. During the investigation of a violent crime, Texas law enforcement officers often conduct live and photo lineups in which an eyewitness is asked to identify the perpetrator out of a group. Unfortunately, eyewitness identifications of suspects are notoriously unreliable.
The problem is a serious one. According to the Innocence Project, a national organization which seeks to free the wrongly convicted, mistaken eyewitness identifications were a factor in over three-fourths of the initial group of 130 wrongful convictions that were later set aside after DNA testing.
According to one researcher, law enforcement personnel need to understand that eyewitness testimony can be contaminated in the same way as physical evidence. Research into the subject has led to some recommendations to reform police procedures. For example, researchers learned that when eyewitnesses are asked to pick the perpetrator out of a group of photos presented all at once, the eyewitnesses tend to compare the photos with each other rather than with their memory. As a result, the recommended practice is now to show the photos sequentially.
Another recommendation is the use of so-called "double-blind" lineups, in which neither the eyewitness nor the officer presenting the lineup knows which person in the lineup is the suspect. This prevents the officer from intentionally or unintentionally influencing the witness's decision.
Whether a mistaken identification is the result of unintentional bias or bad behavior by police, an aggressive defense approach may persuade the judge and jury that the lineup evidence is unreliable. Successfully challenging a police lineup before trial can even lead to dismissal of the charges.
Source: American Psychological Association, "How reliable is eyewitness testimony?" Zak Stambor, Accessed May 15, 2015