As an aside, that raises an interesting question - who's legally liable for the damage to vehicles from me and the bg shooting at each other? Are we each responsible for our own bullets, or is the initial criminal actor responsible for all damages caused as a byproduct of his criminal act? I realize were this circumstance to come up that would be the least of my worries, but I'm still curious.
chicagotex, afaik, in most jurisdictions, the shooter is liable for their own bullets. There was a case, Hall v McBryde, where this essentially came up. Teenager (nongangbanger) went to his parents house to get some items, and some gangbangers do a driveby. Teenager gets parents' gun and returns fire, striking a neighbor. (The neighbor actually went after the parents, claiming negligent supervision, but the parents prevailed b/c there son was not known to be violent.) I don't believe they ever went after the teenager, but the issue of culpability did arise.
The Restatement of Torts (basically a treatise by judges/law professors on what the law should be - state may or may not choose to adopt it) deals with this issue in section 16:
(1) If an act is done with the intention of inflicting upon another an offensive but not a harmful bodily contact, or of putting another in apprehension of either a harmful or offensive bodily contact, and such act causes a bodily contact to the other, the actor is liable to the other for a battery although the act was not done with the intention of bringing about the resulting bodily harm.
(2) If an act is done with the intention of affecting a third person in the manner stated in subsection (1), but causes a harmful bodily contact to another, the actor is liable to such other as fully as though he intended so to affect him.
It is basically the Transferred Intent Doctrine - if you intended to cuase harm to A, but cause harm to B, your intent will carry through to your actions against B and you will be liable for an intentional tort (I'm just talking about civil liability here - criminal liability can be a little different).
I think the analysis would work out like this: BG threatens you, you fire upon BG, striking him, and also strike innocent bystander C. You have committed an assault and battery against both BG and C. You would have a
true defense of self defense against BG, and should prevail provided you meet the criteria for self defense (true defense means
you admit that you did it but...) However, self defense will not work as a defense for your battery against C b/c C was not an imminent threat to you. Moreover, because you intended to shoot BG, this intent will transfer to your shooting of C, making it a battery.
C would also have causes of action against you for negligence, as you have a duty when firing any gun to fire it in a safe manner. This could be used to recover for any property damage, or for personal/physical damages should a battery claim against you fail.
You could try a Justification defense, but this will likely fail. Your argument would be "I was justified in accidently/negligently shooting C because I was being threatened by BG." I can't imagine any court or jury that would allow you to hurt an innocent 3rd party to prevent injury to yourself. Justification is typically used where the damages are not so physical.
I think this makes sense too from a public policy perspective. If you absolve the defender of any responsibility, what is to stop them from going spray and pray style in a crowded area when threatened? This is certainly a touchy issue, and I am on the fence about it. Obviously, I think if you defend yourself and you shoot, a bystander, you did so only because of the actions of the BG. But I think you need to look at the bystander's perspective too. They shouldn't have to endure being shot by you by virtue of you being in danger from BG. Holding you accountable would make you more careful, and thus less likely to hurt an innocent bystander.
Can you tell I have my Torts final tomorrow?