What are you considering "provable?" You know, a judge and prosecutor don't get involved because of suspicion that you have encrypted data that might be usef

What are you considering "provable?" You know, a judge and prosecutor don't get involved because of suspicion that you have encrypted data that might be useful for solving a crime, there are usually a long string of events and circumstances that brings you to that point. The actual encryption keys are just a formality by that point. Whether or not you can plausibly deny the existence of encrypted data in a convincing manner probably isn't going to be that important. Everyone draws a line somewhere and that might be the stand you wish to take, I suspect you'll end up in jail regardless though.