Another magic bullet.
One that just happened to hit in the same spot that a hurried parting shot at the fleeing limo could have hit.
Arlen Spector would be proud of such reasoning.
If you insist there is some conspiracy, I guess anyone will do. From everything I have seen, Oswald acted alone. He had the means and the "motives", as twisted as they were, and all the circumstancial and physical evidence points squarely at him.
If there were some grand conspiracy with a cast of thousands, how the hell did they manage to keep it quite for 44 years? It completly defies logic for anyone not as kooked-out as Oliver Stone.