Alvarez Report

Several years after I wrote the previous sentence, I read a fascinating article in Scientific American by a man who qualified as an expert on the reliability of “eyewitness testimony.” Robert Buckhout wrote:

“Eyewitness testimony is unreliable. Research and courtroom experience provide ample evidence that an eyewitness to a crime is being asked to be something and do something that a normal human being was not created to be or do. Human perception is sloppy and uneven, albeit remarkably effective in serving our need to create structure out of experience. In an investigation or in court. ... [the prosecution and the defense], and usually the witness, too, succumb to the fallacy that everything was recorded and can be played back Iater through questioning.”

Because of the quietness of the acceleration graph between the pulse trains starting at 221 and 313 (except for the pulses which I feel have other explanations), and because of the obvious train of pulses staring at 182, I favor the view that the Commission's "missing shot" initiated this first train of pulses. My best estimate of the time of this shot is therefore 182 minus 5 (for Mr. Zapruder's calibrated time delay), or frame 177.

Anyone who has ever driven a car in a heavy rainstorm, with a slow windshield wiper will realize that a partial loss of visual acuity for a half-second would not seriously affect a gunman's ability to perform good tracking, particularly when most of the car was still clearly visible through the holes in the trees. And if we remember that the decision to squeeze the trigger must have been made a few tenths of a second before the bullet was fired, the effect of the obscuring tree should have been negligible on the actions of the gunman, for a shot fired at frame 177.

I therefore conclude that the accelerations at 220.5 and 221 .5 were caused by Mr. Zapruder's neuromuscular response to an earlier stimulation. If we use Mr. Zapruder's thereby observed oscillation period of about five frames (which is close to the expected value), we place the "wounding shot" at about 215.5.

The Commission based its findings largely on an examination of what the people in the car were doing; President Kennedy "seemed to be reacting (in frame 225) to his neck wound by raising his hands to his throat."

I will ignore the two small accelerations between frames 245 and 280; each is caused by a single frame in which I judged that highlights might be smeared slightly more than the normal smearing caused by the imperfections of the half-tone process. I will return later to the short sequence of significant pulses starting at 290 since they require an explanation. They seemed to me to have less intensity and to last a much shorter time than the three sets of pulses I identified as being triggered by bullets. I eventually found what I think is a reasonable explanation, not only for these angular accelerations, but also for a puzzling deceleration of the President's car at the same time -- but that is getting ahead of the story.

... a previously undetected deceleration of the President's automobile just before the final shot.

I was bothered for some time by the weaker set of pulses lasting a shorter time, that show in Fig. 3, from frames 290 through 298. They don't look like the ones that seemed clearly associated with bullets.

The heavy car decelerated suddenly for about 0.5 sec (10 frames), centered at about frame 299, reducing its speed from about 12 mph to about 8 mph. Since the car was certainly being operated in some low gear ratio, the deceleration was no doubt caused by the driver reducing his foot pressure on the accelerator pedal. The question is then, "Why did the driver suddenly slow down at a time when a more natural reaction would be to speed up and weave to left and right, to avoid being hit again." I worried about this for some time, without finding any satisfactory answer. But then I found some testimony concerning a police siren that was remembered to have come just alter the President was killed (in frame 313).

The many inconsistencies in the various witnesses' remembrances of exact times in this critical period made one feel that it was permissible to suggest that the siren, from an escorting police vehicle behind the President's car, had come a few seconds before the fatal shot. It would be most probable that an escorting officer, having heard one shot, and seeing the President wounded by a second shot, would hit the siren button when I'm suggesting he did. If the siren sound became apparent to Mr. Zapruder at frame 285, we would expect him to respond at frame 290, where we see the "unexplained and relatively weak angular accelerations" starting. We don't know the reaction time of the driver, but if it was 0.5 sec (9 frames), then he would lift his foot from the accelerator at frame 294, as Fig. 7 shows he did. Everyone will recognize that such a reaction on the part of the driver would be an unavoidable conditioned reflex; we all learn that when we hear a siren suddenly turned on just behind our car, we lift our foot from the accelerator pedal. I haven't been able to think of any other reason why the driver or a car that has just slopped one or two high velocity rifle bullets would suddenly slow down his rate of travel.