Posted by
mehavey:
I'm sorry, but that [(unless one has a basis for a reasonable belief that another person would be justified in the use of force to defend himself (that is, was not at fault), one may not lawfully use force to intervene)] is flat wrong.
I'm sure you believe that, but you need to look into it.
In some jurisdictions, one may lawfully use deadly force to defend third persons only if those third parsons are connected with the defender in certain specified ways--spouse, parent, child, etc..
In at least one state, any third person may be lawfully defended though the use of force,
provided that that person would
in fact be legally justified in defending himself--regardless of what the defender may have believed at the time. That was the general rule for a long time.
I described a newer and much more common rule, in which the defender must simply have a
reasonable belief that the apparent intended victim would be entitled to use force to defend himself.
See
this for a general discussion.
The legal right to use force to prevent harm does not exist if a person was committing a crime of violence; if a person had started an altercation and had not made clear his intention to stop; or in the case of mutual combat.