all I'm going to say is 21 ft rule.
you really want to get freaked out, get a buddy, a dummy knife and a dummy gun... see who wins, its very sobering.
21 foot rule is a good rule. Officers can use it. But...in a jury of your peers a gun owner defending himself does not have the same rights of deadly force unless enunciated by the laws of the jurisdiciton you are in. You may do the right thing, you may not even be charged, but agressive anti-gun DA's are going to put a high percentage of righteous self-defense oriented actions in the "bad guy" category and send good guys to jail.
Better to spend my remaining days in jail as opposed to wishing I had done something as the shawdows close in for a dirt nap. Odds of survival go up if one responds to a deadly situation....then it's the odds of the jury and how well you keep your mouth shut after the battle.
My name is, he/them wanted to kill me, his weapon is here, the witnesses are over there, the evidence is over yonder (his empty shells, etc.) and, "I'm sorry officer, you know how important this is. I realize you need a quick statement but I need to speak with an attorney before I answer any questions." Keep your mouth shut...some say the above is too much to say. Officers are trained to realize the physiological affects of a conflict and how it makes them appear euphoric after a shooting and how that is a bad thing for them. But it's "one way" training for most because they are also trained that the quickest statements are the most truthful. Go figure.