I heard it specifically for the USA in at least two occasions. I don't remeber the first, but the latter was in the Brett Jonson's show: in an episode, he talked about another criminal that had some encrypted material and refused to give out the key. He was put in jail until he decided to give it, and at that point IIRC he got an even longer sentence due to the proof he gave them access to. But now that I think about it, it could be that the USA had him arrested by a third country, so maybe some other state's law was at stake. But I would still not bet my safety on it. Even if you successfully appeal it, you would still risk to spend quite some time in prison.

I'm not a lawyer, but from what I remember in the USA the 5th amendment defense works only with some kinds of keys: it works with a password, but wouldn't work with a "pattern" (i.e. Android's option of drawing a pattern by connecting dots) or biometric authentication.

"prove you don't know"

It might be my lack of coffee, but how would that work? You can prove you know something, but how would you prove you don't?