So, I'm curious re: opinions on this - if you were to put yourself in LE's shoes at this point, and we assume that you believe BM to be guilty, but are looking to gather a little more evidence (ideally, a body - but maybe other evidence) before an arrest - would you:
1) Continue to put pressure on BM, to the degree that you could. Make sure he knows you are watching, that you're continuing to press, following leads, digging, etc. - hoping that the pressure gets to BM and he slips up.
2) Or..... you back off, but keep a stealthy eye on BM. You continue to work behind the scenes, but outwardly you let things appear that they are slowing down. Let him breathe, let him think maybe he's going to get away with this - and hope that he lets his guard down and makes a mistake.
3) Something else?