Condit bumped Levy off. I have not a single doubt about it, and have thought so from Day 1.
But he also had help ( his S&M/orgy buddies ) in the coverup!
One of the last clues was that they got an anonymous tip and stopped the search in the park. The tip didn't pan out but they never went back.
So where did the search stop....just a few feet before the area where she was found.