Back to the OP...
In order to draw my weapon the BG has to clearly pose a threat of
great bodily harm or
death. Fair enough.
Let's suppose Mr. BG accosts me in the parking lot of a 7-11 or similar stop & rob, displays a large fixed blade knife or bayonet and demands my money. The lethal threat is implicit in his brandishing the knife. I tell him "Fine! Okay fine! No sweat man!" As I sweep my jacket aside and begin to draw, he gets a clue and realizes what's coming, so he drops the knife and shows his palms, apologizing profusely. Now what?
Well, he's attempted a felony for which I may legally arrest him under the
citizen's arrest doctrine. If I quickly follow up with commands to put him on the ground until help arrives AND he obeys, all is well and good.
I can tell him it's his lucky day and he has 10 seconds to get out of visual range. Let him run somewhere else and count his blessings.
But...
- What if you order him down on the ground and he just turns and starts walking away?
- If you tell him to get lost or start running, what do you do if he decides to simply walk away 50 feet? Or only 30 feet?
- Do you do anything different if he walks off across the parking lot some 50 feet away, then starts angrily cussing you and telling you how he's "gonna whip yo' a**"?
In (1) above, I'm going to keep him covered until he is either out of sight or too far away to be a viable threat, while maintaining a "watch-six" attitude. I may even retreat out of
his sight. It's certain that I will modify my location while his back is turned.
For (2), the obvious answer is to use a cell phone or a nearby phone (if available) to call the PD and have them deal with the guy. Heck, he just may want his knife back.
For (3), the response is about the same as for (2) except that a careful eye is kept on him at all times and for any buddies lurking about.
Home Intruders:
Someone in my home who fails to follow instructions to leave or surrender will leave slightly heavier than he arrived. He may or may not survive his injuries.
In the event that one faces an intruder conveniently in the livingroom and at your first shot they double over, drop to the floor screaming and curl into a fetal position, you are now stuck with it.
Obviously the BG can be faking or not hurt as bad as you think. At this stage, obtaining help is your next step and dialing 911 is second to keeping him covered. SOP says you do what you can to keep out of his line of vision.
If you shoot someone who is down on the ground, I guarantee it will come up in the forensic examination. You'll need a solid explanation for those shots.