A defense layer can "explain away" blood stains on the floor (she cut herself using a knife in the kitchen while preparing food...) and used the mop to clean the blood that spilled on the floor... (you get the picture.)
Unless he involved his femme fatale in the plot or admitted his involvement to her it could be a sticky wicket!
I said from the beginning he was the culprit and that it involved either sex or money or both. Looks like it was both.
I can't imagine how he could have kept the girlfriend(s) secret from Laci forever. He must have given her some lame excuses for his absences and credit card bills. There may have been the obligatory girl friend phone calls listed on the cell phone bills or the mysterious "no one there" house calls and hangups. And of course one can't forget the "gifts" he probably bought her (Laci probably wondered where all the money was going??) and the cost of frequent restaurants etc.
When he used the "fishing" excuse (on Christmas Eve NO LESS!) for the umpteenth time she probably either blew her stack or called him on it or both.
It was crisis time for old Scott. Here he had been stringing this girlfriend along, the sex was great, and hot, and illicit and he just couldn't let that go.
On the other hand (and please pardon me here women of FR) here he was in the prime of his life about to be ball and chained to a wife and kid forever. Laci was petite but her pregnancy had changed her appearance. She wasn't "physically appealing" to Scotty-boy anymore.
And the kid. His whole life and daily routine were about to change. No more running off at every chance to bounce the bedsheets with his lover. Nope. Ol' Scotty would now have to be home the majority of the time changing diapers, nurturing a child he may not have wanted, all the while thinking about that set of 36 D's just a couple towns over.
This may have been an argument that took a decided turn for the worse. One can only speculate but perhaps she slapped him in disgust, or flailed away at him in her anguish. I mean just look at this boy. He's twice as big as her and built like a fireplug from what I can tell. He may have lost it and started beating her and continued until she was dead. Of course there is always a knife here and there in the kitchen that might have come in handy.
Poor Laci. First cuckolded (I know it's the HUSBAND of an adulteress but I thought I would just turn it around) and then murdered in a fit of rage by the adulterer. It's not a pretty thought.
He should have strangled her. No blood. But I don't suppose he was in any logical frame of mind at the time of the killing.
So what do you do with the body? A fresh grave in the valley? After all, some farmer, hunter, hiker might eventually stumble across it even in the the most remote of places. And then there are always the wild animals. You would have to dig the grave very deep. It would take time. You might be seen. It would be risky.
Water hides a body from casual sight. If weighted down sufficiently it will not float or be moved by tides. Only a large scale underwater seach would have a chance of discovering her body. In the dead of night he might have been able to drop her anywhere.
Personally, I'd vote for water. Although the boat and fishing story would help throw the police off the scent if he chose a fresh grave. Always suspect the husband first. It's where the motive is.
I said he probably put her body in a dumpster, outside of the immediate Modesto area.