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Eyewitnesses Accuracy Rises with Level of Confidence


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#1 Greg Burnham

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Posted 22 December 2015 - 11:37 AM

Study Finds Confident Eyewitnesses More Accurate

 

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The accuracy of eyewitness identification of criminal suspects increases with the certainty of the witness in the first test, according to a new study led by UC San Diego researchers.

 

In addition, traditional police lineups that show suspects along with known innocents work best, the study found. The results mean recent legal reforms based on the supposed inaccuracy of eyewitness IDs should be re-evaluated.

 

If confirmed by further research, the study offers a way to improve the usefulness of suspect IDs, and shedding new insight into the system's failures. Numerous studies and reports have found that eyewitness testimony is often unreliable, and the usefulness of this first-hand testimony is continually questioned in criminal cases. 

 

The study was published Monday in PNAS. John Wixted of UCSD was first author; coauthors are Laura Mickes of Royal Holloway, University of London, John C. Dunn of the University of Adelaide in Australia, Steven E. Clark of UC Riverside, and William Wells of Sam Houston State University in Texas.

 

Eyewitness errors are the most frequent cause of wrongful convictions, according to the Innocence Project, a group that seeks to exonerate the wrongfully convicted.

Wixted said the study points to methods to reduce such errors.

 

Real crime data

 

Data from a 2013 Houston Police Department experiment in its robbery division was used in the study. Eyewitnesses were asked to rate their level of confidence as low, medium or high. Moreover, the lineups were double-blind, with neither the eyewitnesses nor the officer running the lineups knowing who the actual suspect is.

 

The experiment found that suspects identified by an eyewitness were more likely to be guilty than those identified by other evidence that didn't include an eyewitness. For those identified by eyewitnesses, 97 out of 114 were (85%) had independent corroborating evidence of guilt against them. For those not so identified, only 67 out of 130 (51%) had such evidence .

 

Researchers led by Wixted and Wells said their results jibe with recent studies of simulated crimes that found eyewitness confidence strongly correlated to accuracy and validated the use of simultaneous lineups instead of presenting potential suspects one at a time.

 

"The significance of our study is that these issues were investigated using actual eyewitnesses to a crime," the study stated. "Recent laboratory trends were confirmed: Eyewitness confidence was strongly related to accuracy, and simultaneous lineups were, if anything, diagnostically superior to sequential lineups. These results suggest that recent reforms in the legal system, which were based on the results of older research, may need to be reevaluated."

 

While memories can become unreliable over time, the first eyewitness assessments are more likely to be accurate, the study found. So instructions to juries to downplay this evidence, such as recently adopted in New Jersey, deprives them of a useful tool.

 

Subsequent eyewitness recollections are less accurate, because they can become contaminated with other information, Wixted said.

 

In cases of wrongful conviction, the eyewitness often first gives an identification with a low confidence level, indicating that the recollection is likely to be erroneous, he said.

"But by the time the case gets to a court of law, there often has been other memory tests in between," Wixted said. "Now the witness is more confidence, because the picture is more familiar, and the police give confirming feedback ... now you're feeling confident. But what everybody overlooked was that at the beginning, they were lacking in confidence."

Other studies must replicate the finding before it can be considered definitive, Wixted said. That means studying eyewitness accounts from other police departments to see if the finding was a fluke or a dependable observation.

 

"No scientific finding is completely trustworthy merely because one person publishes a study," he said.

 

Controls necessary

 

"You get one and only memory test -- it's the first memory test," Wixted said. "On that first memory test, confidence is a highly diagnostic indicator of accuracy. That's the message I tell police officers and prosecutors."

 

However, that test must be administered in a controlled manner.

 

"Critically, our conclusions apply only to fair lineups initially administered to adults in double-blind fashion, not necessarily to unfair lineups, nonblind lineups, lineups administered to children, or to any ID associated with a subsequent memory test (including the one that occurs much later in a court of law)," the study stated.

 

"It is well known that memory is malleable such that by the time a witness testifies at trial or pretrial hearings, an initial low confidence ID can be transformed into a high-confidence ID."

 

The National Academy of Sciences has developed guidelines for eyewitness identification that should be followed, Wixted said.

 

"When you test them that way, whatever confidence they express is telling you a whole lot, don't ignore it," he said. "And just understand it's going to be tainted after that."

 

Source: San Diego Union Tribune [reprinted here for research purposes only]


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Greg Burnham
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"Too often we enjoy the comfort of opinion without the discomfort of thought." -- JFK

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