Just a point of clarification, as this has been posted twice in this thread today.
Max did not have a broken neck.
He had no fractures or dislocations of any of his vertebrae. He had very significant skull trauma, and a 7 1/2 inch sagittal fracture (which is simply enormous, given the size of his head), and he had a very high spinal cord injury (top 2 cm of his spinal cord). His brain and spinal cord injuries were devastating, and produced cardiac arrest at the scene, IMO, on impact. But he did not have a broken neck.
The fall was horrific, and could have happened in seconds. It is absurd to hold Rebecca responsible for that, particluarly when Max's own parents allowed him to play with the scooter inside the house on the second floor. Dina, in an interview, said she allowed Max to play rambunctiously inside the house, and said there were often balls and other "outside" toys laying around inside her home as well. Rebecca may have been in a tough spot-- if Max's -parents approved of letting him play with his scooter inside on the second floor (which it appears they did), and she did not approve, that sets up a confrontational scenario. It's not like Max snuck the scooter inside and upstairs-- he was allowed to have it up there, from every indication. That was an accident waiting to happen, imo.
The minor XZ reported to police that the evening of her arrival Max was demonstrating his scooter prowess to her on the second floor hallway. Which other adults were in the home at that time?
It is absurd, imo, to hold Rebecca responsible for this kind of accident. Kids sneak around and do all sorts of things. Max liked to show off-- it's entirely possible he was showing off a balancing trick with his scooter on the newel post and fell.