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November 13, 2001

Study says police lineups often miss the mark

A new California State University, Sacramento study is critical of on-the-scene, eyewitness identification of crime suspects, and also casts doubt on the reliability of other types of police lineups.

The study, by CSUS psychology professor Bruce Behrman and student researchers, is the largest of its kind ever carried out. It appears in the most recent issue of the Journal of Law and Human Behavior.

Data came from Sacramento city crime records. It was gathered with significant assistance and support from the Sacramento City Police Department, which is intent in improving its lineup procedures.

"Our findings are consistent with the hypothesis, which was that 'field show-ups' may bias the eyewitness," Behrman says. "Most people will identify the suspect as the criminal, and some may do so even in cases where the police decide not to make an arrest."

Behrman and the students examined five years of crime data from more than 700 police lineups. They looked at "field show-ups," in which eyewitnesses identify a suspect near the crime scene, as well as photographic lineups and live lineups.

For each case, they noted the eyewitness response along with a ranking of how much physical evidence police had gathered: substantial, minimal or none. The suspect's eventual trial or release was not considered.

In field show-ups, eyewitnesses identified the suspect as the criminal about 78 percent of the time, regardless of the level of evidence police ever acquired. In many cases, police decided not even to book the people identified by eyewitnesses.

Behrman says that if the field show-ups were truly effective, the percentage of eyewitness identification level should have increased at better evidence levels. The findings suggest eyewitnesses are strongly biased by seeing a suspect in police custody near the scene of a crime.

The study shows photographic and live lineups were better, though far from bullet-proof in court.

In these lineups, 65 percent of eyewitnesses make an identification of a suspect for whom police had "substantial" evidence. Far fewer identified suspects when the evidence was "minimal" or "none." This "real life" finding is consistent with previous laboratory findings made by Behrman and other researchers throughout the country.

However, when just one week has passed, Behrman's team found that eyewitness identification of suspects with "substantial" evidence drops to 33 percent. In other words, memories fade quickly.

The team also found that eyewitnesses tend to be more likely to finger suspects of another ethnic group; victims are no more accurate than other witnesses; and identification accuracy doesn't seem to be influenced by whether a weapon was used.

Behrman, a professor at CSUS since 1967, has been studying eyewitness memory since the late 1980s. He often consults with area law enforcement agencies, and is a frequent expert witness in court. He and his students have just begun another study focused on whether the confidence level of an eyewitness indicates the eyewitness's accuracy.


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