Correct me if this is a normal occurance, but it seems like law enforcement has been especially tight-lipped during this entire case-- not releasing any information about how they obtained the warrant for JM's car, what the type of forensic link was with MH, how exactly the body was found (the searcher attributed intuition and "god," while reports like Barefoot's talk about a tip,) the condition of the body, and the confirmation of the remains as HG has taken a good bit of time considering the press attention.
Just my opinion, but it makes me think that LE's got a whole lot more on JM than any of us are privy to. Maybe he's been someone they'd been watching for a long time in connection to many of these cases, but never had an actual reason for arrest/searches/ etc.