The best of the films is that of Zapruder, and it clearly shows the top of Kennedy's head exploding, and majority of brain matter being blasted upward and forward.
The Itek Corporation, which studied the film closely, pointed out that:
There is no question that the explosion from the bullet impact radiates matter in all directions. The fine matter can be seen surrounding the President's head. However, the major direction of this matter is just forward of the President's head. The major, or large particles which are actually measurable on the film, and have contiguous boundaries which hold together during flight, all radiate in a forward direction [emphasis in original]. ("John Kennedy Assassination Film Analysis," Itek Corporation, May 2, 1976, Lexington, Mass., p. 56)Frames from the Zapruder film after the head shot clearly show the top of Kennedy's head blasted open, with a flap of skin and bone hanging down, and the back intact.
On the other side of Dealey Plaza, behind and to the left of the presidential limo, was Marie Muchmore. Two frames in her film show Kennedy's brain matter being blown into the air. The first is the frame when Kennedy's head explodes.
In the immediately following frame, a red cloud of brain matter can still be seen in the air. The film was broken at this precise point, and is now spliced, but Kennedy's brain matter can plainly be seen going upward and forward.
Finally, a video clip of Patrolman Bobby Hargis, who was riding behind and to Kennedy's left, shows and extreme blowup of the Nix film at the moment of the head shot. You can see a streaming video clip of Hargis (128K ISDN or better connection) by clicking here, or click here to download the clip to your hard drive. (You may need to right-click and pick "Save Link As.") Hargis is usually presented as a witness who proves that the back of Kennedy's head was blown out, but in fact he testified that the head exploded on the right side.