This frame here shows Oswald's back the most, and it's because he was leaning forward at the time.
Is this visual evidence of Oswald being handcuffed behind his back? Is that what we are seeing? And if we're not seeing it, why should we believe it? Should we believe it just because Joseph Backes and Steve Haydon say it? Who are you going to believe? The bloodied bastards or your own eyes?