Read an interview with Innocence Project co-founder Peter Neufeld on misidentification and wrongful conviction:
“The primary cause [of wrongful convictions] is mistaken identification… The second most common cause is the misuse of forensic science other than DNA.”
http://www.slate.com/blogs/blogs/thewrongstuff/archive/2010/08/17/reasonable-doubt-innocence-project-co-founder-peter-neufeld-on-being-wrong.aspx