How China’s Police Used Phones and Faces to Track Protesters

On Sunday, when Mr. Zhang went to protest China’s strict Covid policies in Beijing, he thought he came prepared to go undetected. He wore a balaclava and goggles to cover his face. When it seemed that plainclothes police officers were following him, he ducked into the bushes and changed into a new jacket. He lost his tail. That night, when Mr. Zhang, who is in his 20s, returned home without being arrested, he thought he was in the clear. But the police called the next day. They knew he had…