This is what DoJ wants to close by making just possession of encrypted documents criminal.
(Note: not a lawyer.)
It is? I'm not sure how you'd disprove it. Anecdotally (which I suppose actually matters in this case!) I've had a case where a (fairly long, 26 character) password I used regularly suddenly (and thus far, permanently!) went out of my head. I can remember some fragments of the password but not the whole thing.
The only novel issues encryption brings to the table involve self incrimination, because, AFAIK, IANAL, etc., the only time an encryption key is inarguably protected by the fifth amendment is where the fact that the defendant knows the key is itself incriminating evidence, because the fifth amendment only applies to self-incriminating testimony, not other self-incriminating evidence in the defendant's possession (e.g., the contents of a hard drive, encrypted or not).
So it's business as usual. It's obstruction of justice. Book'em.
And of course, "I can't remember" is always the greatest defense.
This whole thing is about the government endangering the public in exchange for abusing their rights.
It's all bad. You could go as far as argue that the government is obstructing justice and endangering the public by denying basic security.
We already know the enemy will find ways to access all the data. Encryption is not the last line of defense. It's the only line.