And the backward head movement is from...WHAT exactly??
In my opinion, the backwards movement of JFK's head and body from a shot from behind is the most counter-intuitive aspect of this case.
I was originally convinced it was caused by a shot from the right front because it seems so obvious when watching the Z-film.
My reasoning was simple - the immense amount of damage to JFK's head indicates a massive force acted on his head at the moment of impact and this force must be reflected in the way his head moves.
The "back and to the left" motion must surely depict the direction the force acted on his head.
Then I examined this clip of the head-shot very closely:
The following analysis is my own, personal interpretation of what I see in this clip:
The first movement, at the moment of impact, is
forward. This indicates a shot from behind.
The massive flap of scalp, with skull bone still attached, is blown down by the side of his head. To me, this also indicates a shot from behind. A shot from the front would've blown this section of scalp backwards, towards the back of his head (IMO)
A large crater in the top of his head confirms the damage shown in the autopsy pic/Gif above, and highlights the massive amount of force that has acted on the head.
At the moment of impact JFK's head is leaning forward and down, his chin appears to be resting at the very top of his chest.
So, if a massive force was applied to the back of JFK's head while his head was in this forward "resting" position, what would happen?
The very first movement of the head would be forward and down (down, because his head is attached to his neck, so it would move in an arc, not a straight line).
But his head is in this "resting" position, with his chin, more or less, resting on the area at the top of his chest.
This means his head has nowhere to go and is driven into the top of his chest where it experiences an equal and opposite reactive force. It is this reactive force that drives his head backwards and upwards (in an arc).
His head, basically, "rebounds" off the upper part of his torso:
No "jet effect" [what a crock!]
No neuro-muscular reaction [there is zero rigidity in any of his movements]
Just simple physics.