According to Luis Alvarez (HSCA 1:428, 440, 441) the speed of the limo was ca 8mph at the time of the shooting. Here is the testimony from MC police officer Bobby Hargis, riding at the left rear of the limo during the shots:
Mr. STERN. Just a minute. Do you recall your impression at the time regard- ing the source of the shots?
Mr. HARGIS. Well, at the time it sounded like the shots were right next to me. There wasn’t any way in the world I could tell where they were coming from, but at the time there was something in my head that said that they probably could have been coming from the railroad overpass, because I thought since I had got splattered, with blood- I was just a little back and left of-just a little bit back and left of Mrs. Kennedy, but I didn’t know. I had a feeling that it might have been from the Texas Book Depository, and these two places was the primary place that could have been shot from.
Ca 8mph and Hargis got splattered with blood. In this low speeds the splatter doesn’t like ’hang still in the air like a cloud’ while the limo keeps moving forward. It continues with the same momentum as the car until the air slows it down and/or it falls to the ground. Hence no splatter on the following motorcycle if same splatter had no momentum from an incoming bullet exploding it backwards hitting it.
Hargis also says he got hit ”as of a peace of concrete” which is peculiar since none of the three bullets could have produced the necessary recochett for it to happen.
It had to be a bone fragment from the presidents head —-> shot from in front of him.