Just some random thoughts about all this mess...
Just the thought of DM rambling around in that house between the time WM hung up the phone with JC and the time DM himself called for a taxi at 6:11 am, makes me wonder exactly what in the heck he was doing. The "deed" itself would have taken mere seconds. Yet, we're looking at 3 hours.
Not only that, this whole, sick, perverted, wicked act was 100% premeditated. He purposely left the one phone at MS's house. Purposely left his CC for a pizza purchase to be made and made plans to have taxis drive him around so his own vehicle wouldn't be spotted. He needed evidence that he was at MS's the whole time.
Plus, this took place after him and MS brutally ended the life of Laura & made sure she'd never be found. Realistically, what are the odds that MS didn't have a clue what DM was actually doing that night? There's no reason to believe MM had any idea what was going on, but almost zero reason to believe MS didn't know.
Just thinking out loud.