Trent, where you'll be told you're wrong is that many states have some sort of "Castle Doctrine" (as you, of course, know) which, you'll be told, makes the state assume you were in the right and not prosecute you if you claim self-defense.
What that generally overlooks is the fact that all such presuppositions of justification are rebuttable -- meaning that if anything looks at all questionable about your version of what happened, or the independent observer (investigator) doesn't see things the way you see them, the state proceeds with a prosecution, Castle Doctrine or no.
CDs CAN help the righteous defender, and ARE a very good thing. They are NOT any kind of get out of jail free card, or license to do one single thing that you wouldn't do in defending yourself in any other place or situation.
Yes, I've been in many discussions about this very thing, about whether Illinois has "Castle Doctrine", and what it means for justified use of force.
Illinois law, in particular, goes on to read for each of our justified use of force statues the following:
(b) In no case shall any act involving the use of force justified under this Section give rise to any claim or liability brought by or on behalf of any person acting within the definition of "aggressor" set forth in Section 7-4 of this Article, or the estate, spouse, or other family member of such a person, against the person or estate of the person using such justified force, unless the use of force involves willful or wanton misconduct.
Source; (720 ILCS 5/7-1) (from Ch. 38, par. 7-1)
Sec. 7-1. Use of force in defense of person.
Sec. 7-2. Use of force in defense of dwelling.
Sec. 7-3. Use of force in defense of other property.
*If* the use of force is determined to be justified, you are immune from civil procedure from the "aggressor" or any person representing them, unless the use of force involves willful misconduct.
Civil immunity is one thing. But before you can claim that right, the authorities still have to judge you in some fashion to determine if that force was justified.
Having a state's attorney decline to press charges, may not be sufficient for that claim, directly.
Also, some *future* states attorney may decide to prosecute you at any time, especially if new evidence shows up, as there is no statute of limitations on murder. (E.g. 15 years later, a slip of the tongue such as "He got what was coming to him", may turn the tables and bring old skeletons out of the closet.)
I know this thread is about "if you draw, do you fire", which I think has been answered clearly.
But most people -
the vast majority of gun owners - have NO idea what's in store for them if they ever DO drop the hammer on someone. They've never done the homework, read the horror stories of the aftermath, or put much thought in to it, at all.
When I teach concealed carry I try to reinforce the concepts that "firing your weapon is an
absolute last resort,
because it will be a life altering experience for everyone you love and care about."
If the choice is clearly "him or me", don't hesitate. Otherwise, consider your options, there's no "undo" button once you've let lead fly.