There is a very well-thought out essay analyzing self-defense from a legal perspective at
this blog from Colorado Springs Bujinkan I thought worth posting a link to. It critiques the concept of a lethal weapon and points out that if you fire a warning shot or slash at a weapon-holding hand, then you are in a world more legal trouble than if you simply lash out in pure self-defense...realizing of course that you may choose to DO the former but at least don't let on for a moment to anybody that you had that degree of brainpower and of self-control. It also points out that walking into trouble is a whole world different than having trouble walk into you.