Martin’s scenario is possible. They prepared the patsy the be the fall guy. He shows his support for Castro in public. Then, by total luck, he gets a job that puts him in a perfect position to assassinate the President. At a place along a motorcade route that had been used before. In a tall building. In a tall building that is not used as a busy office, as most buildings in Dallas are, but in an old warehouse, with a good chance there would be a floor without nobody (except possibly Oswald) on it. What a perfect coincidence. It would be natural for conspirators to take advantage of such a lucky break.
The problem is, I don’t believe in coincidences. Bad theories commonly have to rely on them. There was a lucky coincidence that made it extra easy or pin Oswald with the crime, making it look like no conspiracy got him in position to commit the crime, because there was no need to. Innocent friends and neighbors had already arranged for that.
Or how about another coincidence. The plotters planted CE-399 to frame Oswald. But they planted it on the wrong stretcher. They didn’t even plant it on a stretcher on the right floor. But they got lucky because someone brought the Connally stretcher downstairs and of all places, parked it next to the stretcher with CE-399. What a lucky coincidence. Now it would be easy to claim the person who brought down the stretcher got the two stretchers confused, which sounds plausible. But wouldn’t sound plausible if Connally’s stretcher was still in another part of the hospital.
False conspiracy theories seem to generate and require lucky coincidences for the conspirators.
Or how about another coincidence. The plotters planted CE-399 to frame Oswald. But they planted it on the wrong stretcher. They didn’t even plant it on a stretcher on the right floor. But they got lucky because someone brought the Connally stretcher downstairs and of all places, parked it next to the stretcher with CE-399. What a lucky coincidence. Now it would be easy to claim the person who brought down the stretcher got the two stretchers confused, which sounds plausible. But wouldn’t sound plausible if Connally’s stretcher was still in another part of the hospital. Or how about this;
the bullet now in evidence as CE399 was never at Parkland Hospital. Tomlinson found a bullet on an unrelated stretcher and allegedly gave it to O.P. Wright. I say allegedly, because there is also a story of Tomlinson giving the bullet directly to a Secret Service agent as witnessed by an OTIS repair man. Anyway, O.P. Wright is on record saying that the bullet he got from Tomlinson and gave to Johnson was pointed. When shown a photograph of CE399 he actually denied it looked anything like the bullet he had handled on 11/22/63.
Tomlinson is on record saying that he was shown a bullet once, for identification, but that was by FBI SAC Shanklin about a week after the murder, yet the FBI claimed that SA Odum had shown CE399 to Tomlinson and Wright in april 1964 and that both men couldn't identify it. Strangely enough, when Odum was asked about this he denied ever having shown any bullet to anybody at Parkland Hospital and/or ever having CE399 in his possession.
The first four persons in the chain of custody could not identify CE399 as the bullet they had handled on 11/22/63. Only SA Todd and SA Frazier indentified it from their markings on the bullet, but those two men didn't get the bullet until after it arrived at Washington.
It is completely possible that an unrelated bullet, found by Tomlinson, was substituted for a bullet fired by the MC rifle (which also was in Washington hours after the bullet arrived) to ensure a "match" between the bullet now in evidence and the rifle now in evidence.
Oh, and btw O.P. Wright's wife was a nurse who attended Connally on 11/22/63. When he heard a piece of metal fall to the ground, Mrs Wright picked it up and found it was a bullet. And Nurse Hill is on record saying that she saw a bullet lying next to Kennedy's head. That bullet mysteriously disappeared as apparently did the bullet that Mrs Wright handled.... It could of course all be coincidence, but then, you don't believe in coincidence, right?