JohnKSa nailed it.
Massad Ayoob teaches the formulation that deadly force is permissible
only "when there is an immediate and otherwise unavoidable danger of death or grave bodily harm to the innocent."
Point by point:
- immediate
- otherwise unvoidable
- danger of death or grave bodily harm
- to the innocent.
The danger must be
immediate. It has to be happening
right now, right this very moment. It can't be (for example) in reaction to someone threatening to come back and kill you next week. It cannot be in reaction to someone threatening to come back and kill you in an hour, or in a few minutes. The danger has to be immediate.
The danger has to be
otherwise unavoidable. If you can deal with the danger in some other manner, you should. If you can run away, if you can talk your way out, if you can go the other direction and never end up in that dark place ... do that. Avoid it if you can, any way you can. Don't willingly get into confrontations either. The danger has to be otherwise unavoidable.
The danger has to be serious: only
death or grave bodily harm count here. A broken fingernail does not qualify. Even a broken bone might not. There has to be a risk that you will
literally die or
be maimed for life if you do not respond with appropriate force. The danger has to be serious.
The danger has to be
to the innocent. If you goad it on, if you "ask for it" or trade insults or otherwise engage in brinksmanship -- you're not innocent! Don't bring it on, don't engage in stand offs, but do everything in your power to defuse the situation before it escalates to deadly force. The danger has to be to the innocent.
If you find yourself in a situation where there is an immediate and otherwise unavoidable danger of death or grave bodily harm to the innocent, deadly force is a reasonable reaction to that danger.
Otherwise? It's not.
pax