I found this testimony about what Paul O'Conner saw while doing the internal chest cavity during the autopsy about the back wound. I think it answers a lot of questions. I've thought for a long time that sniper that took this shot was aiming for the presidents head but it fell short and hit him in the back. And here it is.
A statement made by Paul O'Conner the technician on duty who's job it was to remove the brain of the president and to help Dr. Homes with the autopsy stated this;
Paul O'Conners testimony on the shot in Presidents Kennedy's back.
O’Connor: When we started an autopsy, the first thing we always did…was
to weigh and measure the body. We’d check for any scars, contusions, any
abnormalities, and so on. But in this case, we didn’t turn the body over to
look at the back while we were doing that. Finally we turned the body over,
and there was a bullet wound—an entrance wound—in his back, on the right
side of his spinal column. To emphasize where it was in proximity to the rest
of his body: if you bend your neck down and feel back, you feel a lump and
that’s the seventh cervical vertebra. This bullet wound was about 3 inches
down and an inch or two to the right of the seventh cervical vertebra. I
remember there was a big gush of surprise that nobody actually thought
about turning him over right away, you know after we had done our initial
investigation of the president’s body. Dr Humes took his finger and poked it
in the hole---the bullet wound hole, the entrance wound hole---and said it
didn’t go anywhere. There was a very big argument, a lot of consternation,
that he shouldn’t have stuck his finger in the hole.
Law: What difference would it make?
O’Connor: Well, when you take your finger and stick it into a bullet wound,
you avulse the wound.
Law: You think that happened when he stuck his finger in the back?
Law: It could have create a false track:
O’Connor: Well, not necessarily a false track, as much as a false impression
of the entrance of the missile that went into his back.
Law: Who was arguing?
O’Connor: Dr. Finck strongly objected to Commander Humes doing what he did.
He [Finck] took a sound, which is a probe, a metal malleable, non-rigid probe. We
started out with a rigid probe and found that it only went in so far. I’d say maybe
an inch and a quarter. It didn’t go in any further than that. So we used a malleable
probe and bent it a little bit and found that the bullet entered the body, went
through the intercostals muscles---the muscles between the ribs. The bullet went
in through the muscles, didn’t touch any of the ribs, arched downwards, hit the
back of the pleural cavity and stopped. So we didn’t know the track of the bullet
until we eviscerated the body later. That’s what happened at the time. We traced
the bullet path down and found that it didn’t traverse the body. It did not go in one
side and come out the other side of the body.
Law: You can be reasonably sure of that?
Law: And these doctors knew that?
Law: While it happened?
O’Connor: Absolutely. And another thing we found out while the autopsy was
proceeding, that he was shot from a high building, which meant the bullet had to be
traveling in a downward trajectory and we also realized that this bullet is what we
call in the military a “short shot”. It didn’t have the power to push the projectile clear
through the body. If it had…it would have come out through his heart and through
O’Connor: We were told [in the report of the Warren Commission] that he was
shot in the back and it came out his throat. That didn’t jibe with what we saw, and
when I say we, I’m talking about Dr. Boswell and myself.
. . . . When LAW then showed O’CONNOR the photo of President KENNEDY’s back . . . .
O’Connor: That’s a very accurate portrayal of the entrance wound to his back,
which as you know, is quite a ways down from his neck. At the angle he was
shot…the laws of physics will not let a bullet strike there and go up and go
out his throat…I helped roll him over…one of these arms might have been
mine, because I was at the head of the body and helped roll him over. It
wasn’t rolled over until quite a ways into the autopsy, and that’s when they
discovered the bullet wound.
. . . . O’CONNOR further stated to LAW . . . .
“Now I had this drawing made at the University of Florida showing the back
wound and this is exactly what happened. The bullet struck him in the back,
it passed through the outer layer of muscle and through the inner layer of
muscle between the vertebrae. These are intercostals muscles and they
connect the spinal column together. This bullet came in, arched downward,
and bulged against the pleural cavity, which is the protective cavity around
both lungs. It did not penetrate that lung area. It just bruised it real badly.
I had it highlighted showing there was bruising on the right lung. The back
of the right lung was bruised, but wasn’t torn. It was bruised badly enough
to hemorrhage in the tissues, but not enough to tear the lung or the cavity.”
"and we also realized that this bullet is what we
call in the military a “short shot” I believe that this shot was being aimed at the back of the presidents head but because it lacked the power to penetrate as Paul O'Conner states it feel short hitting him in the upper back.