Dr. Charles Gregory, the Parkland surgeon who operated on Connally's wrist, provided important information on the wounding of Governor Connally in his interview with Dr. Josiah Thompson, Richard Billings, and Ed Kern. After reviewing high-quality enlargements of the relevant Zapruder frames, Dr. Gregory said that Connally must have been hit no earlier than Z234 based on his Z238-242 reactions, that he and Dr. Robert Shaw (Connally's chest surgeon) concluded that JFK and Connally were hit by separate bullets, and that both he and Dr. Shaw concluded that Connally's back wound indicated the bullet had not hit anything else beforehand. Dr. Thompson discusses this crucial information in his 2021 book Last Second in Dallas:
I was already in Dr. Gregory’s office and talking with him when they arrived. I had made photocopies of his deposition, and Kern and Billings had brought with them the four-by-five-inch Ektachrome transparencies from the Zapruder film. I did most of the questioning, and Kern and Billings showed the transparencies on a light table.
After the transparencies were laid out, I asked Dr. Gregory to look closely at what happens between frames 237 and 238, three-quarters of a second after the president has clearly been hit. We moved the other transparencies aside and looked closely at 237 through 240. In this series of frames Governor Connally is turning in his seat to the right. This means that the angle between his right shoulder and the car door gets smaller over time. Then, quite suddenly, it reverses direction and gets larger. What brings about this change in angle is the collapse of Connally’s right shoulder. But that is not all. In frames 238, 239, and 240, Connally’s cheeks puff out and his hair is disordered.
I pointed this out to Dr. Gregory and asked his opinion about what caused it. He explained that the epiglottis is like a trapdoor at the top of the windpipe. A shot through the chest such as Connally received would shock the chest wall and force air upward through the epiglottis. Since it couldn’t all escape from his mouth immediately, it would puff out his cheeks. The three effects we were seeing, Gregory said, were the effects of a bullet driving through the chest.
I asked him what was the maximum time before frame 238 when the bullet could have hit Connally. He thought for a moment and then replied, “A quarter of a second. Maybe 234 at the earliest.” This was generally in line with his testimony before the commission, where he said that “in frames marked 234, 235 and 236, Governor Connally was in a position such that a single missile . . . could have passed through his chest.” Obviously, this was much too late for Connally to have been hit by the same bullet that hit Kennedy. . . .
But there was more.
We mentioned to Dr. Gregory that we had looked forward to talking with Dr. Shaw but that he was unavailable. Dr. Gregory said he and Shaw had talked about the wounding of Connally, and both believed that Connally and Kennedy had been hit by separate shots. Why? Because of the character of Connally’s back wound, Gregory explained. It was small and elliptical in shape. But most importantly, it had very clean edges. No fibers had been carried into Connally’s back wound, while his wrist wound was fouled with numerous fibers from his wool suit.
Dr. Gregory pointed out that he’d been a field surgeon during the Korean War and later had made a study of gunshot injuries, examining more than five hundred gunshot wounds. It was his opinion, supported by Dr. Shaw, that the small, clean and elliptical wound in Connally’s back had come from a projectile that had hit nothing else first. (Last Second in Dallas, pp. 157-158)