36. Summary of the frontal scenarios

Introducing the possibility of a frontal hit makes possible four scenarios: either bullet (from front or rear) exploded the head (did everything), the frontal bullet added momentum while the rear bullet was doing everything, or the rear bullet added momentum while the frontal bullet was doing everything. The solo-rear scenario (sections 8–23) is the only one of these to be fully supported by independent physical evidence and to fully work out mathematically. The solo-front scenario (section 33) fails because of timings and a snap in the wrong direction. The "front adding to rear" scenario (section 34) works because the frontal hit that transfers only momentum adds little enough to the lurch that it can be hidden within the noise of the system. The "rear adding to front" scenario (section 35) fails because it is simultaneously too complex and underdetermined.
Thus two scenarios remain: the rear-only and the front-adding-to-rear. These are essentially the rear-only with a modest addition. The question now becomes whether there is any justification for allowing even a minor addition to the rear-only scenario.
There are two ways to answer this question. The first is to note the absence of independent hard supporting evidence for a frontal shooter or shot. There are no photos of a frontal shooter. No physical traces of any kind were found, including a weapon, empty shells, or fragments in the brain. A shooter on the knoll could not have been missed by the spectators nearby, for everything is very close up there. The second way to answer is to note that a frontal shot violates the extant physical evidence. There was no damage to the left hemisphere of the brain, as would be required from a shot at this angle. There was no obvious second snap of the head, as would be required by a frontal shot passing through the same upper pathway that the first shot used—the quick beginning of the rearward lurch is fully explainable by the physical recoil from the first shot.
Except for the lack of damage to the left hemisphere, a frontal shot contributing only momentum then becomes acceptable but not needed. As far as I can see, it is not excluded physically, however. I happen to think that the argument from lack of damage to the left hemisphere is very strong, but reasonable people may differ on this question. This then becomes a matter to be dealt with by Occam's Razor—if the movements can be explained without the frontal shot and are explained no better with it, we are not allowed to incorporate the frontal shot. Our explanation may consist only of parts that actually "work," that is, that contribute something to the explanation that no other part of it does. Thus we exclude a frontal shooter from the final scenario until positive evidence requiring one turns up, which it has not for nearly 40 years.