The very first frame of the third shot his head does go forward. His head was also turned to the left, that is why the exit was from the right. JFK was also wearing a back brace which prevented him from going forward.
The single bullet theory (actually a fact) has been proven to be very possible in other ballistic tests.
Originally Posted by TheDaliLama
another detail most don't know about. the back brace from his ww2 injuries. many experts including Cyril Wecht think the neck shot .. the so-called magic bullet was a fatal shot in itself. but it's clear Kennedy can't really bend over easily. if he had, the third shot might have missed.
the second shot (of possibly three) whoever it came from was either accidental by the SS or it was insurance by another shooter not Oswald.
the Author of "Mortal Error" cites Howard Donahue, an expert marksman and was one of the few shooters at the time i think the only shooter who successfully fired 3 rounds from that old ww1 Italian rifle in less than 6 seconds.
so Oswald could have fired three rounds. doesn't mean he did. i think he did fire two rounds, where the shot that hit Kennedy in the head came from and who is the mystery.