Depending on where the back wound was actually located.
Well, in order to conclude that it was not in the location shown on the autopsy photos one would have to conclude that the wound location observations and autopsy photos were faked by all three doctors. Is that a reasonable conclusion? Based on what? The location of the hole in the shirt?
By the way, what's the evidence that a gun was fired from that particular location?
For starters, Norman, Williams and Jarman. Also Jackson and Mrs. Cabell and Amos Euins. Then there are the pigeons seen flying from the TSBD roof at the time of the shots. Do you think they were all part of the conspiracy too?
I don't think "proof" makes any sense in legal proceedings -- it's a mathematical construct.. Anything that requires speculation, assumptions, or conjecture is not "proof".
In any fact-finding process (courts, commissions of inquiry or other fact-finding bodies such as NTSB accident investigations) "proof" is another term for evidence upon which people base conclusions of fact. There is nothing absolute about proof.
The only absolute proof is found in mathematics. But proof in mathematics simply shows that an assumption or set of assumptions are logically equivalent to some other statement or set of statements. The assumptions do not have to be true in "reality".