Pardon me if this has been said, but--
Violent criminals who use firearms routinely in COMBAT SITUATIONS will likely be better shots under stress. I have no extensive training, never served, never been in a gunfight- and while I remain a pretty good shot, I know the there's no way in hell I'd be able to outfight anyone with training or experience. Especially the latter.
As I said, I am no expert- far from it. But it would seem like, to me, that the more experienced you are the more calm and levelheaded you are during gunfights. I wonder how much experience you need to use the full extent of the accuracy you produce when not in combat.