[xp38]

I have only read one book on the assassination...Posner's Case Closed. Conspiracy buffs hate it of course but I found it persuasive. In it is the explanation of why the head jerks backwards along with much more fascinating material.

[Swordmaker]

Sorry, if the only book you have read on the subject is Posner's then you are not qualified to make such a judgement. Posner has been debunked by quite a few people who know a lot more than he.