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

Take a look at this frame 228 from the Zapruder film because it is the Poster Child for what is wrong with the Single Bullet Theory. 

At this point, you can see that JFK is struggling from having been shot, but supposedly, Connally had also been shot; the bullet going clear through his chest from back to front, then through his wrist, blasting the head of the radius bone, and then penetrating his thigh. And yet, even though he, supposedly, sustained all that injury, he's sitting there, straight up, totally balanced, perfectly normal, looking straight ahead, and cool as a cucumber, not the least bit perturbed. How could he possibly have sustained all that impact and trauma without reacting to it? Most people go their whole lives without ever experiencing something so horrific. It's a nightmare so bad that most of us can scarcely imagine what it's like, and I'm not sure that I can. But, how long would it take to register in his mind that he is in mortal danger, that he could die? What happens to people in that situation? They experience a spike of adrenaline, and that, in itself, is startling. I expect him to writhe and start opening his mouth. Like this other:

That's Connally reacting to being shot, but not the other. Connally wasn't shot yet in the other. It's all a big lie. And if these people think they can get away with this crappy lie in 2016, they are badly mistaken.