As always, thanks for replying to my questions so quickly and thoroughly. I appreciate your insight.
I've gone back and read parts of your books and listened to the final episode of "In The Dark" again today, and I again find myself wondering how Heinrich slipped through the cracks. I know law enforcement interviewed Heinrich about the Wetterling case in 1989 and put him under surveillance, but did they talk to people that knew him? How much did they really put him under the microscope? They had footprints, tire tracks, and found police scanners at his dad's home. That evidence was circumstantial and not scientific, but I think it was at least strong enough for them to put serious pressure on Heinrich.
Yes, they needed evidence and probable cause to bring forth formal charges, but they didn't need those things to simply knock on a few doors and ask people what they knew about this guy. I haven't read or seen anything to suggest that they did so.