A study led by an Iowa State University psychology professor has found the presentation of photos of suspected criminals has an impact on the error rate of eyewitness identifications.
Gary Wells says the data shows having witnesses view photos one at a time, otherwise known as the “sequential” procedure, produces fewer mistaken identifications than “simultaneous” photo lineups.
The study found witnesses identified a “known innocent filler” nearly 42% of the time under the simultaneous procedure compared to 31% 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.
The Des Moines-based American Judicature Society issued the report today and set up a media conference call with Wells and other researchers. Wells believes when witnesses are asked to look at suspects simultaneously they tend to compare the lineup members and decide who looks most like the perpetrator.
“So, the theory is that the sequential lineup prevents the side by side comparison process and instead forces witness to use a more absolute comparison of each lineup member to their memory, rather than compare lineup members to each other,” Wells explained. 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 eyewitness identification remains a significant problem. “In D.N.A. exoneration cases, for instance, 75% of those who were exonerated with forensic D.N.A. tests, after being convicted by juries, are cases involving mistaken eyewitness identification,” Wells said.
He’s hoping the report will encourage more law enforcement agencies to switch from simultaneous to sequential lineups. The full study is posted on-line at: www.ajs.org.