Oswald in the doorway: the blog of the Oswald Innocence Campaign, by Ralph Cinque

Notice on JFK that we can see the point of his right shoulder.

You see the seam of his right shoulder, right? And I'm pretty sure that he wore suits that fit him. Therefore, we can say that the camera visualized the point of his right shoulder. And the same is true even more so of Jackie's right shoulder. We can see the seam going across the garment, and you can see the right shoulder there plain as day. But, what about their left shoulders? JFK's is out of view. His head is obstructing it. So, we can't see the point of his left shoulder. We know he's got one, but we can't see it. And on Jackie, I would say the same; we are not seeing the point of her left shoulder. By the "point" I mean the most outward point where the vertical part of the shoulder meets the horizontal part. And keep in mind that it tends to be softer and rounder in women, and more squared off in men. 

Let's look at Jackie from the front.

That is presumably the same suit but a different day. So, you see how far the edge of the collar is to the point of the shoulder. 

Let's compare the two:

So, how much of the span on the right are seeing on the left? Not much. It certainly isn't showing us the point of her left shoulder. On the left, we are seeing a little smidgen past the edge of her collar. 

That is all we've got, and there is no basis to claiming to see the shoulder point or the upper arm.

So, the situation is that we can see her forearm, but we can't see her upper arm or the point of her shoulder. 

But, we do have an idea where the point of her shoulder is, and looking through our mind's eye, we can "see" it. We know very well where it belongs. But, how is that forearm getting to it?

Not even the mind's eye can help with that when her face looks farther away than her forearm. How could her left shoulder possibly be connected to that forearm? What path is her upper arm taking to do that?