Last I looked at it, it was like having a safe. They can take the safe and break in.

If the safe is locked by a key. They can subpoena a key since it’s a physical object. It’s something you have, not something you know. If you’re phone is locked by biometrics, it’s something you have. They can force you to give them something you have.

If the safe is locked with a combination, they cannot force you to talk. You have the right to remain silent and the right not to incriminate yourself. If your phone is locked with a pin or passcode, it’s a similar concept.

However, things get murky, because if we stay with the safe analogy, and they know you have a specific document or item in that safe. They can subpoena that specific document and you may be compelled to provide the document, although maybe not the combination.

Anyway, long story short. Shit is weird and not cut and dry.