What happens if a cop forces you to unlock your iPhone X with your face?

Imagine you've been detained at customs, waiting to cross the border. Or maybe you've been pulled over for a traffic violation. An officer waves your cellphone at you. “Look at this. Is this yours?” he asks. Before you can respond, a tiny infrared sensor in the phone has scanned your face. Matching those readings against the copy of your face that is stored in its archive, the phone concludes that its owner is trying to unlock it. The device lowers its defenses, surrendering its contents in moments to the law enforcement officer holding your phone. “You have to work pretty hard to get me to put my fingerprint on a reader,” said Chris Calabrese, vice president for policy at the Center for Democracy and Technology. “You have to work less hard to put a phone in front of somebody's face.”