31. Introduction to a frontal hit

    The common view of JFK's rearward lurch is of course the "obvious" one—that it comes from a hit from the front or right front. A pure frontal hit seems very unrealistic because it would have had to originate on or near the bridge, where a shooter would have been exposed to general view. So that scenario didn't happen. More acceptable—at least in theory—is a hit from the right front, with the shooter standing behind the stockade fence at the corner or to the left of it. I happen to think that this scenario is totally unrealistic on its face, for the grassy knoll is a small place and all the people up there were too close to each other to have missed a rifle, to say nothing of a shot from it. One need only visit the place to see how cramped it was. Nevertheless, it is instructive to test the scenario physically, that is, to see whether a shot from the knoll had enough momentum and energy to produce the observed lurch.
    A little thought shows that this course is not as straightforward as it might seem, however. The physics is, but finding the appropriate scenario is not. The simplest scenario would involve only a bullet passing through the head
—no explosion, cloud, or large fragments to deal with. This is the sort of scenario that one might envision as a second shot quickly following a first shot from the rear. The first shot would account for the quick forward lurch, the cloud, and the large fragments, but not the initial rearward lurch. Although this scenario is nonsensical (the cloud and fragments would account for the lurch and thereby leave little or no room for the second shot), the physics of a simple hit can at least be considered.
    Another scenario could involve a shot from the right front, but allow it to produce the full suite of effects—the snap, the cloud, the large fragments, and the lurch. This scenario has the advantage of being simple, at least in principle—a reverse version of the rear hit doing everything. It has fatal problems, though, the two main ones being a snap in the wrong direction and insufficient time for a lurch.
    A third scenario would be the overt combination of a rear hit (doing everything) followed immediately by a frontal hit (adding only momentum). This is the version proposed by Josiah Thompson in Six Seconds in Dallas. The rear hit snaps the head forward, then explodes the head and creates the cloud and the two large fragments. Its proponents do not claim that it also creates the lurch, but this monograph shows that it must create a sizeable lurch. The frontal hit then simply adds momentum to the lurch. The question here is what happens when these two scenarios are combined into a single set of equations, not just considered separately.
    There is a fourth scenario where a first bullet from the rear creates only the forward snap. It is followed by a bullet from the front that creates everything else (cloud, large fragments, and lurch). This is close to the scenario advocated by James Files and Robert Vernon. The problem is that Files's scenario invokes a cloud to the rear, which is contrary to the fact that it went to the front. Files refers to debris over the trunk, whereas it covered the front of the car instead. So we can't take this scenario seriously. We can modify it slightly, however, by keeping the forward cloud.
    We begin with these four scenarios.

    32. Scenario 1—no cloud or large fragments
    33. Scenario 2—cloud and fragments as observed

    34. Scenario 3
frontal hit right after rear hit
    35. Scenario 4—rear hit provides only snap

Ahead to Scenario 1—no cloud or large fragments
Back to Grand Summary of Constraints

Back to Physics of the Head Shot