But, since he most likely didn't set the alarm when he was loading or unloading, there is a POSSIBILITY that she, a curious 7 year old, would find it hard not to disobey the rules, cross the street, and go in there to explore, even like Goldilocks, try out the bed to see if it was "just right".
If he had to go answer the phone, or head into the house for some other reason, and was delayed in coming right back out, it wouldn't have taken her long to check out the motorhome, and leave some evidence.
This, to me, is what is meant by reasonable doubt. But, I want to hear all the evidence before making up my mind. I am not opposed to the death penalty, but want to be pretty sure of the evidence before sending Westerfield to the chair.