Policing

Chinese cops are using facial-recognition sunglasses. Here’s how that tech works.

Facial-recognition technology is no longer a gimmick in dystopian science fiction movies or CSI-style cop shows: It’s increasingly used in more pedestrian ways. Your face can unlock your iPhone X, for example. Or, if you’re flying with Jetblue from Boston to Aruba or the Dominican Republic, you have the option of using your visage as your boarding pass, a system that involves an offsite U.S. Customs and Border Protection algorithm making the matches. And now, the tech—featuring a camera attached to sunglasses— is being used by police officers in crowds in China, The Wall Street Journal reported on Wednesday.

In addition to the glasses, the Chinese system involves a connected mobile device that the police officers carry that contains offline face data, allowing the system to work quickly. According to the Journal, at one city’s railway station, they’ve nabbed seven people associated with crimes using this method, as well as others traveling under false identities.

Here’s how artificial-intelligence-powered technology like this works in general—and what one potential pitfall of it is. (Besides, you know, the whole surveillance-state thing.)