It doesn't sound like a death penalty case.
For future reference:
Utah 76-5-202. Aggravated murder
http://www.le.state.ut.us/~code/TITLE76/htm/76_05028.htm
Utah 76-5-203. Murder
http://www.le.state.ut.us/~code/TITLE76/htm/76_05029.htm
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.