Again please list those witnesses that claimed they heard echos?
Firstly, I have already given you one.
Secondly, perhaps you can tell us exactly how you expect the sound of a gunshot echo to differ from the sound of a gunshot?
Thirdly, perhaps you'd care to explain my own personal experience, already recounted, of hearing the shots from a single location coming from various directions depending on where I was relative to the shooter?
Fourthly, perhaps you could explain how Connally and Kennedy were shot in the back by someone in front of them?
Fifthly, perhaps you would care to explain your contention that Kennedy was shot in frame 189 of the Zapruder film, despite his total lack of reaction to it.
What evidence do you have, that discerning the direction of shots in Dealey Plaza would cause the majority of a given population to have a distorted but unified experience all recognizing the direction to be from the exact same location.
That's physics, but I don't expect you to actually understand that, despite your profession to having multiple science degrees in your previous incarnation on the old board.