This is a sad one; I’m afraid we’re looking at more police malfeasance.

Police in Wales are claiming that their face-recognition system has been working pretty well in the last 9 months; they have arrested over 450 people.

The problem is that their facial recognition system has a 92% false positive rate. [ars] I’m afraid they are missing the point: it gives the police an excuse to stop and question anyone, anytime.

A “false positive” isn’t even (quite) the right term. If you’ve got a test that returns true or false, a “false positive” is when the system returns “true” and the test is not true. For something like facial recognition in a police application, the correct test is not true/false, it’s:

Who is this? Is that person wanted for a crime?

Presumably, what they are describing is a false identification. The way Ars describes it:

New data about the South Wales Police’s use of the technology obtained by Wired UK and The Guardian through a public records request shows that of the 2,470 alerts from the facial recognition system, 2,297 were false positives. In other words, nine out of 10 times, the system erroneously flagged someone as being suspicious or worthy of arrest.

Did the system mis-identify passers-by as Max The Pirate, wanted for piracy on the high seas? Or did it correctly identify the passers-by as who they were, and incorrectly flag them as “stop and frisk!”? There’s a really bad failure mode hidden in there: the system appears to be identifying a lot of people incorrectly but it’s identifying them as someone worth a stop and frisk. That’s highly suspicious; I’d expect the system to identify someone incorrectly, then fail. I.e.: “I don’t know who that is” which never leads to a “stop and frisk.” Someone is lying.

In other words, the cops are just lying. The facial recognition truck is a way of having an excuse to pull over anyone based on the inaccurate recognizer; they could just replace it with a camera that rings “ding dong” whenever it sees motion. Time for an ID check!

Wait ’till LAPD gets their hands on one of these. They’ll just shoot everyone they see and say “it said ‘shoot on sight.'” They’ll love that.

“Of course, no facial recognition system is 100 percent accurate under all conditions. Technical issues are normal to all face recognition systems, which means false positives will continue to be a common problem for the foreseeable future,” the police wrote. “However, since we introduced the facial recognition technology, no individual has been arrested where a false positive alert has led to an intervention and no members of the public have complained.

Nobody has complained? I doubt that. But perhaps the population is just so happy that they’re not going to get shot, that they are grateful to escape.