In Virginia, the answer is that if you have armed yourself in reaction to a threat the inference of malice that the use of a firearm in a homicide carries is negated. The same rule probably carries for lesser offenses such as malicious wounding, but the cases which set the rule are homicide cases. Generally, this has been laid out in a series of decisions having to do with jury instructions. The best statement of this probably comes from Bevley v. Commonwealth, JUN46, VaSC No. 3097:
It is a fundamental doctrine that a person who has been threatened with death or serious bodily harm and has reasonable grounds to believe that such threats will be carried into execution, has the right to arm himself in order to combat such an emergency. Whether the threats were made, or the accused had reason to believe they would be carried into execution, were questions to be determined by the jury. However, when a jury is told that the law presumes that a person using a deadly weapon to kill another acts with malice and throws upon the accused the burden of disproving malice, then the accused is entitled as a matter of law to have the jury instructed that he has overcome the presumption, if they believe the evidence offered in his behalf.Of course, this uses the old "presume" language, which we have scrapped nowadays in favor of telling juries that they can infer. Nevertheless, the principal in the decision is still sound.
This right to arm extends so far that in Jones v. Commonwealth, JAN48, Va. No. 3304 a man who was clearly threatened could go home, arm himself, and wait on his porch for the man who threatened him to come was entitled to the right to arm instruction.
There are some limitations to the requirement that the instruction be given. Reasoning that the right to arm instruction is based upon a need to counter the available inference that if someone purposefully arms himself the act of doing so indicates malicious intent, the Virginia Court of Appeals has stated the instruction is not appropriate when the defendant merely grabbed an available weapon to defend himself or his family. Lynn v. Commonwealth, MAY98, VaApp No. 0109-97-3. I take this to mean that since the defendant didn't purposefully seek a weapon there is nothing to counteract from the purposeful seeking of the weapon and therefore, the only instruction needed is the self defense instruction - not the right to arm instruction.
So, what exactly is the instruction? Well, here's the one from Bevley:
The court further tells the jury that when a person reasonably apprehends that another intends to attack him for the purpose of killing him or doing him serious bodily harm, then such person has a right to arm himself for his own necessary self-defense."And here's the one that was rejected as unnecessary in Lynn:
When a person reasonably apprehends that another intends to attack him or a member of his family for the purpose of killing him or a member of his family or doing him or a member of his family serious bodily harm, then such person had a right to arm himself for his own necessary self-protection and the protection of his family, and in such case, no inference of malice can be drawn from the fact that he prepared for it.The second covers all the bases, so I think it's the better of the two.
It's an interesting line of reasoning and carries all sorts of questions. Does the threat have to be individualized? Can a Blood carry a sidearm because he knows that the Latin Kings are trying to kill Bloods in the City? The cases refer to the right to arm. How does this right play out with felons or others who are forbidden by mere laws from possessing firearms? Can a felon carry a firearm if he knows that the Pagans are hunting him? Personally, I think there has to be an individualized threat which has some immediacy.