This is an important constitutional issue! The subject may be deplorable, but the root issue is not. If it is a "foregone conclusion", then they should have no problem convicting the guy without forcing him to testify against himself. If it is not a "foregone conclusion", then they have been lying and are illegally (unconstitutionally) depriving him of his freedom for months, without even charging him with a crime!
It is not in fact settled law that unlocking an encrypted drive is testimonial. It's also worth remembering that the primary motivation for 5A is to prevent false, coerced testimony and torture; when SCOTUS eventually deals with this, they could find that no protected substantive rights are threatened by demands to unlock encrypted media. We're unlikely to get it both ways: both a right to strong encryption without g…
I know for myself, even with passwords I use multiple times a day from memory, it only takes a couple of months of not using them before I cannot recall them again. This guy has been locked up for 7 months.
See also the numerous people who stored bitcoin in brain wallets (bad idea), who now cannot reclaim their money despite considerable financial incentive to do so.