The Harris County (Houston) District Attorney’s office has a unit devoted specifically to identifying innocent people in prison and letting them out. That leaves about 2900 D.A.’s offices that don’t.
One way innocent people get to prison is the “line-up” or “photo spread” in which a victim or other witness is asked to identify the perpetrator from a group of six people, or six photographs. That creates a strong impression that the perpetrator is somewhere in the group, and there’s overwhelming evidence that someone – whoever looks most like the actual perp – is likely to be selected. Once that happens, everything pushes the witness toward more and more certainty about the identification, no matter how spurious.
It turns out that there’s a different way to do the identification process: give the witness a set of photos, or a group of people, to look at one-by-one, asking in each case, “Is this the guy?” In experiments, this approach is less likely to lead to a positive identification, which is why police and prosecutors don’t like it. But the different between the two techniques consists entirely of false IDs. Yet such is the muscle of law enforcement in the political system that most states still allow, and most police departments still use, the “six-pack” process, with its predictably high false-positive rate.
So innocent people continue to lose large chunks of their lives to false verdicts based on eyewitness ID. How many? If the rate of false conviction were 3% – which I would regard as an insanely optimistic number – that would be 50,000 people doing hard time for stuff they didn’t do. It’s hard not to get angry.