Describe the last person who served you a coffee. What if I helped refresh your memory? Showed you some photos of local baristas? Pulled together a helpful lineup? Cheered exuberantly when you picked the "right" one? Now imagine that instead of identifying the person who made your venti latte last week, we had just worked together to nail a robber or a rapist. Imagine how good we would feel. Now imagine what would happen if we were wrong.

Last month, a Texas judge cleared Timothy Cole of the aggravated sexual assault conviction that sent him to prison in 1986. Although his victim positively identified him three times—twice in police lineups and again at trial—Cole was ultimately exonerated by DNA testing. The real rapist, Jerry Wayne Johnson, had been confessing to the crime since 1995. Unfortunately, Cole died in prison in 1999, long before his name was cleared.

Our eyes deceive us. Social scientists have insisted for decades that our eyewitness identification process is unreliable at best and can be the cause of grievous injustice. A study published last month by Gary Wells and Deah Quinlivan in Law and Human Behavior, the journal of the American Psychology-Law Society, reveals just how often those injustices occur: Of the more than 230 people in the United States who were wrongfully convicted and later exonerated by DNA evidence, approximately 77 percent involved cases of mistaken eyewitness identification, more than any other single factor.