It doesn't sound like a death penalty case.
He planned it out well in advance. The story about going to medical school was to explain his leaving Utah. Either just before leaving, or on the road, he would kill her, dump her body, and pop up in a third location, neither Utah nor North Carolina, to be caught soon thereafter. Apparently, he panicked when he found out that she knew he was lying about medical school, and she had told co-workers about the call. So, he still killed her, but he went into some stupid "Plan B" mode -- as if Plan A wun't dumb enough.
He was scheduled to go to NC a few weeks before her, ostensibly to 'set up shop' before wifey-poo came out.
I don't know if he meant to eventually kill her in NC or even kill her at all. He didn't seem to be the motivated type--made $8.50/hr., hung out at the mini-market when he should have been in school, looked like he was putting on the poundage--so maybe the 'good life' to him was the whole college charade--pretend he's a student while his wife and family support his sedentary lifestyle. The only way he could perpetuate that scam was to cook up the med school story and execute it. He probably had visions of lime Camels, mini-market hot dogs and 96 oz. Humongo Gulps dancing through his head when Lori got the fateful phone call and the bubble popped.