Hurchel Jacks, driver of the VP car carrying Vice President Lyndon Johnson and Lady Bird Johnson gave his position at the time of the first shot as follows:
"My car had just straightened up from making the left turn . I was looking directly at the President's car at that time . At that time I heard a shot ring out which appeared to come from the right rear of the Vice President's car." (18 H 801 - the statement is part of CE1024).
We cannot see any of the VP car after z180 and it is hardly discernible after z177. But Zapruder frames z1 to z64 show a motorcycle making the same turn. Assuming that the motorcycle is moving at approximately the same speed as the motorcade, the motorcycle turn should give us a reasonable idea of the number of frames required for a vehicle to make the turn.
We start with the first frame z1 which compares to the VP car position at z133:
The position of the motorcycle 23 frames later at z23 is similar to the position of the VP car at z163 which is 30 frames after z133:
The position of the motorcycle 13 frames later at z36 is similar to the position of the VP car at z172 which is only 9 frames after z163:
I would suggest that the position of the motorcycle at z59 is the earliest frame in which one could conclude that the motorcycle had completed the turn.
There are different ways to estimate the frame at which the VP car was in the same position as the motorcycle at frame z59. 58 frames after z133 is z191. z59 is 23 frames after z36 so 23 frames after z172 is z195. But since z172 is 39 frames after z133 and z36 is 35 frames after z1, the VP car may have been moving a bit slower than the motorcycle was. That would mean that z59 should be equivalent to 58 x 39/36 = 63 frames after z133 or z196.
On the other hand, moving between positions seen in z23 and z36 for the motorcycle took only 9 frames for the VP car - so maybe after z163 the VP car was moving faster than the motorcycle after z36. Projecting that faster speed through to the VP car equivalent position to z59 would be to add (9/13) x (59-36) = 16 frames to z172 which puts the VP car in the same position at z188 (as the motorcycle at z59). So the estimated range is anywhere from z188 to z196 as the possible range for the VP car completing the turn. And Jacks said it was just after that, not before.
All the occupants of the VP gave statements that are fully consistent with Jacks' statement that the car had completed the turn and was moving along Elm at the time of the first shot. None of that fits with an early first shot miss, even without SA Youngblood's recollection after the first shot: " I noticed that the movements in the Presidential car were very abnormal and, at practically the same time, the movements in the Presidential follow-up car were abnormal".
