RICHMOND, Va. (AP) -- The greatest cause of wrongful convictions stems from innocent people being misidentified as criminals -- including several notable cases in Virginia.

Experts say eyewitness errors happened in 75 percent of cases in which defendants were later exonerated.

To address the problem, Virginia's Department of Criminal Justice Services has overhauled its model policy on police photo lineups and eyewitness identifications. The agency is encouraging police departments to adopt the standards and is training officers on best practices and the importance of following strict witness-identification standards to preserve the system's integrity.

The guidelines call for double-blind lineups, meaning the investigators don't know suspects' identities so they can't give any inadvertent or direct clues. Also, all mug shots in a lineup must be of a similar format so they don't bias a witness.

AP-WF-07-05-12 0647GMT