Continuing our little epistemological exercise:
To move the needle of history would require (1) a central FACT for which the LN narrative simply cannot account, and (2) an explanation that convincingly accounts for that fact.
The needle of history will never be moved by a mass of "Oh, yeah, what about THIS?" sort of stuff in which MTG and many CTers specialize. That is simply "Oswald defense counsel" mental masturbation. It goes nowhere, except in the dark halls of Conspiracy World.
Cliff Varnell at the Ed Forum is on the right track with his claim that it is "impossible" for the LN theory to account for the alignment of the back and throat wounds and the holes in the jacket and shirt. The problems are that (1) the alignment, while highly problematical, has too many "ifs" to really qualify as flat-out impossible, and (2) Cliff's explanation (CIA-issued ice bullets) doesn't strike most people as convincing. But he's basically on the right track.
The critical FACT for which the LN narrative cannot account would almost surely have to relate to the physical evidence of Dealey Plaza. It's conceivable a startling document or two would do it, but documents have so many possible problems that it would be unlikely. (I happen to be reading a scholarly study of the Salamander Letter that rocked the Mormon Church in the 1980s but turned out to be a clever forgery.) It's possible that the technology available today could show that the bullet trajectories posited by the LN narrative are simply impossible and that at least one bullet had to have come from the Dal-Tex or County Records building, as John Orr is attempting to do - that would do it, although the defenders of the LN paradigm would kick and scream to the bitter end precisely as Thomas Kuhn described. Again, however, such work would have to show that the trajectories posited by the LN narrative are IMPOSSIBLE, not simply problematical.
Until then, the LN narrative will stand as the only explanation that qualifies as a legitimate theory.