During his interview with Brit Hume (the transcript of which can be found easily on the Internets), Cheney said that when the accident occurred, he was hunting near one other hunter (obviously Pam Willeford) and a guide (probably Bo Hubert) and/or an "outrigger." Cheney was on the group's "far right." (Or so he thought. In fact, unbeknownst to him, Whittington to was to his right.) The setting sun was to the group's right (which can only mean they were facing south).
Cheney told Hume that a quail then went up and flew towards the west. Cheney took aim at the bird, then pulled the trigger, shooting towards the sun (the west), inadvertently hitting Whittington.
Persons hearing this Hume interview probably assumed (very reasonably) that Cheney, while following the bird, had simply turned to his right (clockwise) and spun perhaps 90 degrees before pulling the trigger.
But look at the police report that summarizes Deputy San Miguel's brief 2/12/06 interview of Cheney. (It's posted at the Smoking Gun Web site.) That reports indicates Cheney told the deputy that the quail went up "behind" him, and he then turned in a "counter clockwise direction" before shooting at the bird.
Assuming Cheney told Hume the truth, and assuming Cheney told the deputy the truth, and assuming the deputy accurately recorded what Cheney had told him, then the only logical conclusion we can reach is that Cheney, while following the quail, turned to his left, then spun around about 270 degrees before shooting low towards the west, striking Whittington.
The fact that Whittington got hit on the right side of his face and neck seems to corroborate, not contradict, this 270-degree spin theory. Allow me to explain. If Willeford, Cheney, and Whittington were standing in a roughly east-west line, facing south, with Willeford to Cheney's left and Whittington to Cheney's right, and if a quail then goes up behind Cheney, and if Whittington then hears and/or sees (out of the corner of his eye) the quail, his natural reaction would be to turn his head (if not his whole body) to his left roughly 135 degrees (three-quarters of a half turn) so that he would then be looking directly at the quail behind Cheney. Such a turn would expose the right side of his face to Cheney. If the quail then flew in Whittington's direction, and if Cheney pulled the trigger just as the quail was flying in front of or behind Whittington, Cheney's birdshot would hit the right side of Whittington's face and neck.
From a hunting-safety point of view, Cheney's biggest gaffe was pulling the trigger without first making sure there was no person in his line of fire. But the 270-degree spin that he apparently made just before he pulled the trigger was nearly as big a gaffe. It was reckless. It was a gross violation of an important hunting-safety rule: when hunting with others, don't spin to the point where you are pointing your gun at one or more of your companions. As Cheney made his 270-degree counterclockwise spin, he almost certainly pointed his loaded shotgun at Willeford and the guide and/or outrigger, thus placing them in danger, at least momentarily.