This question arises from time to time, much like Christoper Lee in the old Dracula movies. Once again, let me attempt to drive a stake through its heart.
Determining the level of consciousness of someone who isn't shamming can be difficult, even if one is trained and experienced.
Determining the degree of incapacitaion can also be difficult, even in some one who isn't shamming.
Here is what you know:
1. Moments ago, you believed the BG to pose a threat which justified the use of lethal force.
2. He now appears to offer no threat.
What you do not know:
1. What is his level of consciousness?
2. Is he incapacitated?
3. Where are his weapons? Even if you see one, you can't rule out the presence of more.
4. Does he have an accomplice?
5. If he is unconscious, how will he respond if he regains consciousness?
Given what you don't know, I maintain that there is absolutely no way that you can approach the BG in relative safety.
Even with trained back-up, approaching him may be quite dangerous.
How safe would it have to be for me to approach the guy? It would have to be completely safe. No ethical issue can reasonably require that you risk your life for one who just put you in fear of your own life.
I haven't even addressed the practical problems to approaching him, because I wouldn't even consider approaching him voluntarily.
For instance, do you take your weapon, and leave yourself vulnerable to a disarm? Or do you leave your weapon behind? Neither sounds attractive to me.
Distance is your friend. Maintain it.
Do you just let him bleed out? No, don't do that. Keep your distance, stay behind cover, and call 911.
I am a physician. My hospital is a level one trauma center. I deal with injured people routinely, including gun shot victims. I deal with unconscious people daily.
I've been doing this for 20 years, and I can't tell by looking at someone from across the room if they have ceased to be a threat. If I can't tell, who do you think can?
I've dealt with many gun shot victims, to include rifle wounds to the head, that would have still been a threat if they wanted to be.
My oath does not require me to risk my life to provide aid to the BG.
Might this look bad to a jury? It might, but I can explain it. If I approach the guy, and some joker sees me rendering aid and thinks I'm finishing him off, that might look bad to a jury, too, especially if he dies. And if the jury believes his testimony, then I'm on the hook for murder 1.
Why shouldn't the jury believe him, anyhow? The jurors might think it's far-fetched that I'd put myself in danger to rush over and save the guy I just shot. I certainly think it's far-fetched, and I'm always amazed when people suggest this.