One of the more insane aspects of our criminal justice system is that structurally speaking it treats convicting innocent people of crimes they didn’t commit as a kind of close substitute for convicting the guilty. As Mark Kleiman explains, our most routine police procedures are designed to ensure that someone takes the fall whether or not the cops actually have the right guy:
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.
Personally, I tend to consider myself a pretty “tough on crime” person. Indeed, I’d say that in the wake of the 1990s crime drop, the United States has become unduly complacent about a level of violent crime that’s still extremely high by international or historical standards. I also think people tend to underrate how socially costly that high crime rate is. But punishing innocent people is not an effective crime control strategy.