Here's the thing. I firmly believe only a sociopath/psychopath (whether there's a difference is another argument) is capable of eraser killings, which is when one spouse kills the other rather than divorcing them. Psychopaths are generally very intelligent too, so its not some guy in a wifebeater hollering STELLA and waving his Bud can around.
Josh Powell. I don't know how intelligent he was, but he wasn't a doofus. He hadn't been arrested, not enough physical evidence. Maybe NO physical evidence. Circumstantial, yes - wet spot in the rug and fans blowing at it, that sort of thing. He obviously did it. We know now he obviously did it. What would the case against him have looked like?
There are patterns, attitudes, ways of being, ways of behaving and ways of viewing other human beings. Brothers from another mother, all cut from very similar cloth. I'd dearly love to come across just one eraser killer who kept it in his pants, just so I could change my world view up a little for kicks. The patterns are there, the similarities all align and can be disussed ad nauseam, but there's no point really because people will say Oh, just because JY is guilty doesn't mean BC is guilty.
So just because these guys are smart doesn't mean they need to go round getting free passes for murder. Just because we, as regular human beings, can't fathom their minds and find it impossible to believe, doesn't mean they haven't done it. Whatever it is. Googled a dump site, thrown some HP's away. They're a different breed.