A court can order a criminal suspect to use their fingerprint to unlock a phone – and it's not a violation of their Constitutional rights.
That's what the Minnesota Supreme Court said Wednesday, in which it ruled on a question that hasn't been touched by the U.S. Supreme Court, or any other state supreme court up to this point.
The case involves Matthew Diamond, who was arrested in 2014 in connection with a burglary. Authorities got a warrant to seize and search his cellphone, and when they needed Diamond's fingerprint to unlock it, a judge ordered him to give it.
The state used texts, phone calls and cellphone ping data during the trial to make its case, and Diamond was found guilty.
But Diamond appealed.
He argued, in part, that being forced to give his fingerprints was essentially the same as making somebody testify against themselves – which they can't do. That's why the whole "plead the 5th" thing exists.
What the ruling says
The Minnesota Court of Appeals didn't see it Diamond's way in its ruling from January 2017. And neither did the state Supreme Court, which upheld the appeals court's decision.
The basic question is: If investigators used data found on Diamond's phone – only unlocked because he was ordered to use his fingerprint – as part of the case, does that amount to Diamond being forced to incriminate himself?
The answer is no, the state Supreme Court said (you can read the full opinion here).
That's because the 5th Amendment only protects a suspect from "testimonial communication," actually offering something up knowledge from their mind.
Providing a fingerprint to unlock a phone is simply presenting a physical characteristic, similar to "standing in a lineup or providing a blood, voice, or handwriting sample."
In addition, the "act of providing a fingerprint to the police was not testimonial because the act did not reveal the contents of Diamond’s mind."
So, no Constitutional violation.
What about a passcode? That's trickier
The Minnesota Supreme Court has said using your fingerprint to unlock a phone isn't forcing you to give up something you know. It's a conclusion other judges around the country have come to also, as The Atlantic wrote about.
But what about your passcode?
As the Consumerist wrote, judges in Michigan and Virginia have ruled suspects can not be required to give phone unlock codes. That's because it's forcing the suspect to communicate knowledge – which is possibly self-incriminating.
A new wrinkle is the facial recognition scanning unlock technology the iPhone X touts so much.
That seems like it would fall into the same category as providing a fingerprint. But no court has actually ruled on it.
According to a Washington Post story from September of 2017, the final answer to that simply isn't known.
“Ultimately, this is the next development in the already existing, open legal question," Susan Hennessey, managing editor of Lawfare, told the paper.
There is a way to quickly disable an iPhone's biometric unlocks. As Wired reports, iOS11 has an "SOS" mode – if someone taps the home button five times in quick succession, it will disable TouchID and/or FaceID (depending on the model) and revert back to a passcode lock screen.