I'm still curious, what kind of evidence or testimony might be considered believable in this case. Whether someone remembers a particular sequence of words and symbols seems like a thing that's very hard to determine, and by its nature it's unlikely there is any evidence either way.
From the quote you give (and I'll admit I have not read up on this case beyond the article, so it's possible I'm missing something), it sounds like he claimed he didn't remember the password, the court responded with "I don't believe you because you haven't proven that you don't remember it, so have fun in jail until you decrypt."
How would you prove, if you were brought into court, that you don't remember a specific password?