Otherwise, the only thing this does is add one extra step ( and additional cost which doesn't matter since taxpayers are footing the bill ) for the Feds to break into your phone.
It's unlikely this ruling will be upheld since providing biometrics to unlock a phone is difficult to construe as 'testimony' since it's performing an action, like complying with a court order to unlock your front door in response to a warrant should you not desire for the police to kick said door in.
The biggest gray area currently is whether typing in a password is 'something you do' or 'something you know', and you can find different precedent to support both conclusions in US jurisprudence for the time being. Hopefully SCOTUS will come down on the side of 'something you know' if/when such a case ever makes it before them.
Agreed, feels like this rises and falls with the forced blood draws issue that was decided in the 60s [0]. Maybe if you claim the phone isn't yours, unlocking it with your face or password would be testimonial? Not sure if that defense would survive them calling the number that was registered to you.
It seems pretty clear to me that a password is 'something you know', whilst a fingerprint is 'something you are'. Moreover, typing in a password is very clearly a communicative act, whilst placing a finger on a scanner is a lot more murky. It might communicate intent, but it can't communicate ideas.
Maybe things change if you need to know which fingers work.
And it is not just an extra step. Cracking an encryption is infeasible or extremely expensive when properly encrypted.
This depends highly on your threat model. What your local sheriff's office can do, versus the FBI, versus the NSA. Mall security Rent-A-Cops can peek through an unlocked phone, but probably aren't going to be doing any kind of cracking other than the obvious possibilities.
The question is whether they can legally do that without a warrant. And if this ruling stands, they'll basically be required to get the warrant if they want access to your device (unless you're naive enough to just hand it over unlocked).