MSD

Considering the glasses that guy wears, his depth of field probably isn't particularly good. When firing at a target moving at the speed of a bird that has been flushed out of a bush, a 28-gauge at full choke (probably tighter than what he was using,) with the shot measured at 20 yards is not simply going to fire a nice circle of shot, but rather leave a trail about 15 feet long in which a target may be hit.

edit: I should also mention that a shotgun is much more precise and accurate than the general population believes (you cannot simply point it in the general direction of the target.) While entertaining, the "Cheney Shotgun Experiment" neglects the fact that the gun was in motion, and does not take into account the fact that shot distribution is not uniform and is not consistent from shot to shot (multiple shots with a more accurate recreation of the circumstances of the accident/conspiracy would settle this.) I would say that the most certainty I could put behind an analysis is that it is 90% likely that the distance between the gun and Mr. Whittington was between 10 and 60 yards at the time he was shot.

I'm not saying you're definitely wrong, but I'm saying that the official explanation is possible and that I consider it probable, while I consider your version of events to be highly unlikely. Neither is entirely implausible, and I would not rule out incompetence/drunkenness or malice based on my knowledge of Cheney. Before arriving at certainty, I think it would be wise to wait and see if any more facts or bits of information surface, that is, if the mainstream media outlets don't forget about it and move on to whatever shiny object catches their attention next.