If LE honestly thought DR did it, they would have found something of substance in 2010 and he'd be trialed and jailed by now. They wouldn't let him continue teaching students and roam the community. They've had 25 years to arrest him, and they've never done so. They haven't even arrested and released him (unlike SOMEONE ELSE...hmmm)
Whomever does solve this case will be a hero in MN. If they had enough on DR they would have arrested him years ago.
I can tell LE believes DR is the guy. I'm sure they have thoroughly discussed what they have with prosecution and know they don't have the obvious things needed to press the charges. The BCA agent asking DR to confess tells me exactly who is on their "radar".