Flutterby™! : Change line-ups

ABC News: Police Lineups Need Overhaul, Study Says

“Mistaken eyewitness identification is the primary cause of the conviction of innocent people,” said Dr. Gary Wells of Iowa State University. “If you look at, for example, DNA exoneration cases where DNA came along and was used to test claims of innocence…three out of every four of those exonerations are cases of mistaken identification.”

Basically, if you show the witness everyone at once, they'll pick out the person who looks most like the perpetrator. If you show them people individually and say "is that the perpetrator?" you'll get a yes or a no, but are far less likely to get a false positive.