Wow, what a can of worms. Glen E. Meyer is right when he says get a lawyer. One jurisdiction will adjudicate far differently than it's next door neighbor. Ditto for each and every incident, even within the same juristiction. And let's not even get into civil liability! Expect to be sued, be prepared for it, and then if by some miracle it doesn't happen, you're a happy camper. Now, having said all that, let me go out on a limb and throw out the following as a suggested guideline for the use of deadly force: "Only when faced with the threat of immediate and inescapable death or great bodily injury". There are some great folks out there involved with lethal threat management training. Seek them out. Stay safe.