The reality is as it always was- IE:"tie goes to the shooter" which also means until convicted in a court of law......Hmmmm
Actually, a claim of self-defense is what is known as an "affirmative defense"; unlike the regular innocent-until-proven-guilty standard applied to a criminal act, the onus in a self-defense shooting is on the
shooter to demonstrate that the shooting WAS indeed justifiable, unless you were defending your home or (in some states) being carjacked, in which there may be a presumption of justifiability. In other words, in a self-defense case, the standard is "guilty unless shown innocent," and if the shooting is questionable, it is much more likely to swing against the person claiming self-defense than it is to swing in their favor.
The general criteria that must be met for a homicide to be ruled justifiable are very similar in every state. The best phrasing I have found so far is in Steve Johnson,
Concealed Carry Handgun Training, North Carolina Justice Academy, 1995, pp. 3-4, but these criteria would apply in pretty much every state.
(1) Justified Self-Defense
A citizen is legally justified in using deadly force against another if and only if:
(a) The citizen actually believes deadly force is necessary to prevent an imminent threat of death, great bodily harm, or sexual assault, AND
(b) The facts and circumstances prompting that belief would cause a person of ordinary firmness to believe deadly force WAS necessary to prevent an imminent threat of death, great bodily harm, or sexual assault, AND
(c) The citizen using deadly force was not an instigator or aggressor who voluntarily provoked, entered, or continued the conflict leading to deadly force, AND
(d) Force used was not excessive -- greater than reasonably needed to overcome the threat posed by a hostile aggressor."
(Emphasis added.)
Note that ALL FOUR conditions must generally be met in order for a shooting to be ruled justifiable (there is an exception for someone kicking your door in, but we'll get to that in a minute). A handful of states used to add a FIFTH criterion to the list above, that of running away from the imminent lethal threat before turning to defend yourself (and hoping the attacker doesn't kill you while your back is turned). Florida was one of those states, and eliminated it with the new law; most states have never had such a provision to start with.
It should be clarified that reasonable belief does *NOT* mean merely "feeling threatened"; the phrase is a legal term, and its definition in the context of self-defense law is that in paragraph (b) above--i.e., that "the facts and circumstances prompting that belief would cause a person of ordinary firmness to believe deadly force WAS necessary to prevent an imminent threat of death, great bodily harm, or sexual assault." Merely "feeling threatened" isn't reasonable belief; the belief has to be objectively rational, i.e. there is in fact a guy standing in front of you holding what appears to be a knife in a threatening posture.
There are a few other conditions that may constitute justifiable self-defense; for example, there is a provision in U.S. legal tradition called the Castle Doctrine that says that if someone is making an illegal forced entry into your home (whether by door or window, whatever), you are authorized to use whatever force is necessary to stop them and it would ordinarily be ruled justified; the presumption is that if the guy is kicking your door down, he's not there to sell magazine subscriptions. A majority of states explicitly spell out the Castle Doctrine in their laws, I believe, but the principle is there in every state, even Massachusetts. Florida, and most other states, also allow the use of lethal force to stop a "forcible felony," i.e. rape, aggravated assault, armed robbery, etc.