I wouldn't get that type of insurance, unless I had a lot of assets to protect, or unless I was particularly trigger-happy, because just HAVING the policy is an invitation to a lawsuit in the event of a shooting (or at the very least, make the prosecution of the civil case against you turn much more VIGOROUS upon the plaintiff discovering the existence of the policy, even if the initial litigation is started without the plaintiff knowing the existence of the policy, which is bad news particularly if the policy limits don't cover the amount of damages, in the event you're found liable - not justified in using self-defense/deadly force), and particularly if you have a lot of assets to proect. That's really the key in the decision of whether or not to carry such insurance, is what kind of assets you have, and are they in any kind of protected form (such as a trust). True enough that the prevailing attitudes of the likely jurors in your blissninny state are relevant as well, but it don't matter if you have little or no non-exempt assets. In that case, the cost of the premiums ain't gonna be worth it, esp. considering how unlikely it is that you use a gun in self-defense. True that guns are used defensively in the US some 1.5 - 2 million times a year, but in most of those cases, shots are never fired, and even the ones where shots are fired, many are never prosecuted, as they are clear self defense cases. Plus, there's some 270+ million folks in the US, vs. 2 million defensive gun uses. That's a 0.7% chance per year of you using a gun in self-defense. It's gonna be lower in low crime areas, but higher in high crime areas, but that's an average.
But to answer your question re civil vs criminal liability: In theory, your defense to the criminal charge (self-defense) will also fully sustain you as a defense to the civil charge (self-defense) - the civil claim will be for wrongful death or mayhem or battery and/or assault, depending on whether the "victim" lived and other facts. But self-defense is a defense to both the criminal and civil claims/charges, in the 2 separate proceedings (if it comes to that). If you can establish the defense in one, you should be able to establish the defense in the other. HOWEVER, even though YOUR burden of proof for establishing your defense of self defense is the SAME in both proceedings (in theory - a preponderance of the evidence), the plaintiff's burden of proving the claim or charge is much higher in the criminal matter than in the civil matter - but this probably won't matter one bit in reality, however, in most self-defense scenarios, because in self-defense scenarios, your defense is NOT the "OJ Defense", or what I like to call the "SODDI" defense - "some other dude did it", aka "wuddn't me". So the plaintiff's/state's case will be easy to show in both proceedings equally easily (death of a human; you did it; allegedly wrongfully). The key is the strength of your self-defense claim, which must be shown by a proponderance of the evidence, that a reasonable person, in your shoes, given ALL of the facts and circumstances, down to every last nitty gritty detail, would have been in fear (reasonable fear) of death or serious bodily injury. This thus invokes the right to use deadly force. The details of this vary from state to state, but it's basically that in all states. There are other jury instructions that vary from state to state on the defense of self-defense, most notably whether one does or does not have a duty to retreat. In most Western U.S. states, for example, WY, NV, UT, MT, etc., IIRC, you do NOT have a duty to retreat before using deadly force, even if in reasonable fear of death or serious bodily injury. In most all states besides these, however, you DO have a duty to first retreat (escape), IF possible, before using deadly force. Also, most states allow you to use deadly force to protect yourself or a loved one, but states are split on whether you can use deadly force to protect a stranger (someone other than yourself who is not a 'loved one'). Also, in states that have a so-called "make my day" law, the defense of self-defense is EASY to establish (in both the criminal and civil cases) just by making a "prima facie" case of: (a) you being in your home (residence), (b) the "victim" is an uninvited guest (an intruder), and (c) you actually fear (not REASONABLY fear!) any potential harm to you or loved ones (not just deadly or serious harm!). Much easier to establish the prima facie self defense defense. Once that's done, the self-defense justification is PRESUMED, and then the state (or plaintiff) has the burden of proof of rebutting the presumption of self-defense - not easy to do. This usually does NOT extend to the entire "curtilage" or homestead, but only inside the primary dwelling/living quarters. I forget how many states have a "make my day" law, but I want to say it's about 2/3rds or maybe even 3/4ths of the states. I know mine has had it since 1987. Now in cases where the issue is not self-defense - where one uses the SODDI defense, then the OJ cases clearly demonstrate the 2 different results that can obtain from civil and criminal liability from the same actions (alleged) of the defendant. In OJ's case this was about 50% due to the lower burden of proof by the plaintiff in the civil case (proponderace vs. beyond reasonable doubt), about 25% due to the superior skill and financial resources of the plaintiff's litigators (relative to Marsha and Chris), and about 25% due to the composition of the jury. Most of the time, a difference result would be more like 75-90% attributable to merely the difference in the standard of proof. In any event, OJ ain't real relevant to the discussion, as that was not a self defense claim, but it does show the stark difference in outcomes possible in civil and criminal charges stemming from the same actions (alleged).