Dr. Spitz was
clearly wrong about much (not all) of what he has stated. Your quote can be found within
this article from March, 2000. In it, he claims to have "
reviewed more than 100 autopsy photos which have never been released to the public," and yet he makes the preposterous claim that, "
it was perfectly rectangular. That piece of bone that was knocked out, remained attached on a hinge,and was bendable." Granted, he may have seen other photos that we do not have access to, but in the one autopsy photo of her skull that was leaked you can plainly see that
the shape of the missing piece of skull was elliptical. Further, it does not have a single piece of bone attached on a "hinge" that was "bendable". The single "piece of bone" was described in the autopsy as a "comminuted fracture". From Wikipedia:
A depressed skull fracture is a type of fracture usually resulting from blunt force trauma, such as getting struck with a hammer, rock or getting kicked in the head. These types of fractures, which occur in 11% of severe head injuries, are comminuted fractures in which broken bones are displaced inward.
(There is a photo on that page (skull fracture) showing a depressed skull fracture with comminuted bone.)
Seeing Spitz's "work" in the Caylee Anthony and Phil Spector cases, I don't see a reason anyone should even look to him for real answers. (BTW, that's him in the avatar I'm using now showing how the blow was struck. Try pushing the end of a flashlight into clay or mud and see if you can get an impression shaped like that of JonBenet's depressed fracture.)