The circumstances are moot, due to the fact that a threat can occur in many different forms. Regardless of the form of the threat, or the instruments used by the threat, either the threat meets the intent/ability/immediacy criteria necessitating the use of force/deadly force, or it doesn't.How do you determine if the use of force is unlawful without considering the circumstances?
3rd party defense is not my focus, nor is it my job to defend them (anymore). However, IF, (and that's a big if) I were to ever interject myself on the behalf of a 3rd party, I would use the same criteria.It's easy if you're the victim, but what if it's a 3rd party?