Police can force you to use your fingerprint to unlock your phone

The Fifth Amendment, which protects people from incriminating themselves during legal proceedings, prevents the government from compelling someone to turn over a memorized PIN or passcode. But fingerprints, like other biometric indicators—DNA, handwriting samples, your likeness—have long been considered fair game, because they don’t reveal anything in your mind. (Marcia Hofmann, a digital-rights lawyer, wrote a comprehensive rundown of the question in late 2013, when it was still hypothetical.)

Now that it’s clear that police are willing to ask for warrants for phone-unlocking fingerprints—and that judges are willing to sign them—security-conscious smartphone users are faced with a menu of mostly unsavory options.

A fingerprint and a long passcode provides a good balance between convenience and security—or it did, until courts began compelling fingerprint unlocks, said Chris Soghoian, the chief technologist at the American Civil Liberties Union. The alternatives are worse: A short PIN “lets you use your phone like a human,” Soghoian said, but can be guessed by a computer algorithm in certain cases. And a long passcode, while secure, is a pain to type in every time you want to check Tinder.