There is a significant change in JFK after z193:
The change may begin before z193 if the change in right hand is part of the reaction:
The only change in JFK after Z193 is he quit waving at the people to the right. There's lot's of footage of JFK not waving at various points in the motorcade. Why would anyone think that is significant.
Several witnesses put the first shot when JFK was between the lamp post and the Thornton sign (z190-z200).
I'm sure everyone's immediate reaction to the gunshot was to take note of the limo's position on Elm St. <chuckle>
