...the evidence in support of the fatal head shot coming from the front is overwhelming... Witnesses that described the shot to JFK said a cloud of wound debris flew back and to the left.
Warning: Gory details which some people might prefer to not read.Going back to this one, Profmunkin, have you examined frames 313 to 316 of the Zapruder film?
Frame 313 shows a large red cloud forward of JFK's face and obscuring Jackie's face. Above it and slightly to its rear is a whitish cloud. In a full-frame version you can see what looks like the trail of something which appears yellow against the green grass and is flying upward and forward in a straight line, about 15 degrees from vertical. It seems to pulse four to six times in the one frame, indicating it may be of irregular shape and rotating swiftly. Being visible in only two dimensions, it could be flying parallel to the car, toward the camera, or away from the camera, but it certainly appears to be moving forward. It is also visible on page 108 of the Warren Report.
In frame 314 the red cloud has subsided substantially, but the white one is still visible although it has dispersed a little, and there is a hint of the yellow object a little higher than in 313, but still travelling in the same upward, straight and forward direction.
Frame 315 shows the white cloud dispersing further and there is a yellowish object higher still, almost in line with the spectator's feet, although this could also be one of the many artifacts on the film.
Frame 316 shows the white cloud dispersed even more.
This sequence, which would have occurred in about four-eighteenths or 0.22 of a second, could indeed be showing the effects of a shot from the rear and not from Zapruder's right, which, as has been pointed out, would possibly have hit Jackie.
The frames can be viewed, numbered and uncropped, in the Medio Multimedia CD-ROM "J.F.K. Assassination - A Visual Investigation" (1993 - made for Windows 3.1). They can also be seen unnumbered and cropped, so the yellow object isn't shown, in the part-fictional movie
JFK, at around 2:34:37, chapter 36, in the 3:01:06 copy of the film, when Costner does his "back and to the left" thing.