The 5th amendment?

I'm not sure why you are being downvoted for this, unless you are being interpreted as snarky (whereas I interpret you as offering a noncommittal answer).

While it has not been settled in court yet, IIRC, the 5th amendment right against self-incrimination is the legal rationale used to argue against forced decryption [1].

[1] https://www.eff.org/deeplinks/2013/10/new-eff-amicus-brief-a...

I was tentative because the direction that two centuries of case law has taken the bill of rights often surprises me.

Thanks for the link. I googled for a bit to see if there had been a decision by the Massachusetts Supreme Judicial Court, but it doesn't appear so.

I watched a bit of the oral argument [1] from last November, and the state's argument was that since they were only asking for an order for the defendant to decrypt the data (not hand over the decryption key), the the defendant's 5th amendment rights would not be violated.

[1] http://www2.suffolk.edu/sjc/archive/2013/SJC_11358.html

The point here, if I'm not mistaken, has to do with search warrants and what evidence is admissible in court.

Lots of things. Namely, they can't prove that you are even able to.

Sure they can. When they find your fingerprints on it, your name on the bill, people willing to testify that they consider the number that the phone is associated with to be yours, etc.

It's not bulletproof like some sort of mathematical proof, but the law operates with much looser standards of proof.

I didn't say they can't prove the phone belongs to you. They cannot prove that you know or remember the decryption key.

Additionally, in U.S. case law there is a precedent for 5th amendment protections applying to being forced to reveal encryption keys:

https://www.eff.org/press/releases/appeals-court-upholds-con...

What if I implemented a dead-man's switch so that if I don't respond regularly, it will be impossible for me access data?

Then there's the case of destruction of evidence. Depends on a number of circumstances, possibly including whether or not it takes a positive act or merely the lack of an action, on your part, to ensure the data continue to exist.

There are so many things that can be done digitally that bump up against the first, fourth, and fifth amendments as well as laws about the destruction of evidence. It's a mess.

Are you asking what would actually happen if you did this, or what would happen if you told the courts that you could not let them into your phone because you did this?