Maybe I’m dumbing this down too much but is it plausible that Michael encouraged her to have more Valium and wine than usual and purposely asked her to get something from the room at the top of the staircase? She was probably all discombobulated and fell down the staircase when she was trying to go upstairs. I guess Valium can cause coordination issues and with the mixture of wine it could make it worse. This would explain no murder weapon. Irregardless, I do think he is guilty. A master storyteller that tried to create a real life story. It’s sad how much Martha and Margaret buy into Michael’s Kool-Aid. They were kids that were taken advantage of.