Could be. Just imagine the possibility that the guy wised up and told her “I’m breaking up with you. I can’t take this anymore.” He basically drives away, and she hooks up with a predator. No one knows about the predator. He buries her in the desert. The boyfriend is totally screwed. Maybe he didn’t do anything, but he’s 100% in prison for life.
Not if they never find a body and he has a halfway decent attorney. Simply too much room for reasonable doubt.