This is about the only way I'm ok with what they are doing. If this is the case, then I'm 100% ok with compelling him to unlock the drive for the sole purpose of accessing those files. Anything else on the drive should be off limits as it then becomes testimonial.
To me the danger is, what if this person committed other crimes and by unlocking the drive he give the prosecution info about those crimes. In a world where the investigators and/or prosecution have gotten away with parallel construction I wouldn't expect them to play fair. I mean, realistically it sounds like they guy is guilty as sin. That being said, I'd rather he get away with those hypothetical crimes than we start allowing situations like this to happen.
So, to recap, make him unlock to read the known files (by exact path) and nothing else on the drive.
To me the danger is, what if this person committed other crimes and by unlocking the drive he give the prosecution info about those crimes. In a world where the investigators and/or prosecution have gotten away with parallel construction I wouldn't expect them to play fair. I mean, realistically it sounds like they guy is guilty as sin. That being said, I'd rather he get away with those hypothetical crimes than we start allowing situations like this to happen.
So, to recap, make him unlock to read the known files (by exact path) and nothing else on the drive.