Even though SM was a petite woman, carrying a dead weight of even a 100 lb person would be exhausting in those conditions. He may have taken a trail partway on his ATV and then carried her in a ways. The problem with this is that the trails in that area seem to get heavy use. The weather was getting warm in May and the scent of decay would be strong.
If you look at the dirt road that leads from PP to the RV park on a satellite map, you will see that a set of power lines parallels that road. Usually those power lines have an cleared area underneath them that is pretty well maintained so service workers can easily access them if need be. If you look south of the power lines, you will see hundreds and hundreds of acres of heavily forested land. It would make more sense for BM to follow those power lines for a ways in an ATV and then veer off into the forest to find a dump/burial site in the middle of the night. I think he knew better than to have his phone with him when he did this. Plus this is not an area where people would be hiking or ATVing by.
He would have to take his phone with him when he left for Broomfield on Sunday morning and he wouldn’t want LE to pinpoint stops along the way. He was specific that he left home at 5:00. I’m sure he made sure that he checked into his hotel around 8:00 so he could say that SM was alive when he left and he went straight to the hotel. He said in one of his few statements that he was at the hotel and he didn’t do anything wrong there. He stated there were “cameras everywhere”. In his mind it was the perfect alibi. He didn’t count on the fact that LE can not say definitively that SM disappeared after 5:00 am on Sunday morning. Furthermore, we have no idea what he did all day on Sunday.
MOO