Well Opinions, this is pretty much a given that it is murder.  Not sure why you are putting that big IF in caps at the front of your post.  The article states that the state crime lab has determined the cause of death to be a homicide.   And people don't kill someone in self-defense, and then dump their body in a remote area.

Apparently, going by this news report, the only thing that has not yet been proven beyond doubt is whether this body does indeed belong to Bundy.   One would think that could be done with DNA analysis.   However, that often takes a long time to get tested.