I think one of Carradine's ex's stepped forward about the whole thing, though my memory of the event is fuzzy. But practically speaking, I would imagine the crime scene investigation would reveal more than the autopsy...lubricant would likely be nearby, there'd (hopefully) be a means to...erm, clean up...things like that. He probably also had some means of stepping down nearby which, tragically, failed. The devil in the details, I suppose, is the point that tips the scale from one to the other.