Jim on Nancy Grace said that marty was thrown out of the church
Yeah, that would be a given, considering what he's already admitted to/been convicted of (a felony conviction is almost automatic excommunication, if I am not mistaken).
That said, I'm guessing his membership in the church was only important to him, as it pertained to maintaining his standing in the community. Even if, for argument's sake, he didn't kill Michele, he's still done plenty of stuff that a faithful member would try to avoid. And, he seems to do it with no remorse. Well, his standing in the community is pretty well shot, regardless of what happens in the next 72 hours. From a church standpoint, he either doesn't care, or is so calloused, it's not important to him.
From an LDS theology perspective, murder is pretty much the end of the road, as it pertains to your eternal perspective. With it, you've ended what Mormons feel to be supremely important, our mortal life (and the opportunity it provides us to be tested, and to grow). There is no, "Oh, Jesus will forgive you!" Jesus
could forgive you, but you would be incapable of repaying the person who's life you ended.