By Kay Henderson
DES MOINES, Iowa (Reuters) - The method by which photos of suspected criminals are shown to witnesses can affect the accuracy of identifications, with photos shown in a sequence producing fewer mistakes, a study has found.
Gary Wells, a psychology professor at Iowa State University who was the study's lead researcher, said presenting photos one at a time, in a sequence, produced a lower error rate than when witnesses were shown a simultaneous array of photos.
Wells' study found witnesses identified a "known innocent filler" photo 18 percent of the time under the simultaneous procedure compared to 12 percent under the sequential procedure.
"We believe these results go a long way toward instilling greater confidence in the sequential procedure as something that improves the reliability of eyewitness identification evidence," Wells said in a conference call with reporters.
The Des Moines-based American Judicature Society issued the report on Monday.
Wells said that when witnesses were asked to look at suspects simultaneously, they tended to compare the lineup members and decide who looked most like the perpetrator.
The theory is that the sequential line-up prevents the side-by-side comparison process and instead forces witnesses to use a more absolute comparison of each photo to their memory, rather than compare lineup members to each other, Wells said.
The national study, conducted between 2008 and 2011, involved police departments in Austin, Texas; Tucson, Arizona; San Diego, California; and Charlotte, North Carolina.
Wells said mistaken witness identification remained a significant problem.
"In DNA exoneration cases, for instance, 75 percent of those who were exonerated with forensic DNA tests after being convicted by juries are cases involving mistaken eyewitness identification," Wells said.
He is hoping the report will encourage more law enforcement agencies to switch from simultaneous to sequential lineups. The full study is posted online at www.ajs.org.
(Writing and reporting by Kay Henderson; Editing by Mary Wisniewski and Cynthia Johnston)