You lock your phone so other people can't access it. But how you lock your phone is an important factor in whether law enforcement can compel you to unlock it. Apple's year-old Face ID system[1] is no exception. On Sunday, Forbes reported[2] the first known example of law enforcement anywhere using a suspect's face to unlock a phone during an investigation.
The question of whether cops can force someone to unlock their phone in the US for a search hinges on Fifth Amendment protections against self-incrimination—that no one "shall be compelled in any criminal case to be a witness against" themselves. Privacy advocates argue that this extends to the act of unlocking a phone or generally decrypting data on a device. But while that line of thinking has succeeded as a defense against having to produce a passcode, it works less reliably in the context of Touch ID or other biometrics. Something you know, like a passcode, is easier to view as testimonial—legally speaking, a statement made by a witness—than something you have, like a physical attribute.
"Big picture, a warrant is required for the search of a device except in certain circumstances at the border," says Greg Nojeim, director of the Freedom, Security and Technology Project at the Center for Democracy & Technology. In the newly reported Face ID case, police did have a warrant to compel 28-year-old Grant Michalski of Ohio to unlock his smartphone, and Michalski has gone on to face child pornography charges.
"The next question is whether a person has a right against self-incrimination in providing the tool that law enforcement would use to search the device—a password or a fingerprint or a face," Nojeim says. "For the issue about whether you can be compelled to