“self-defense” is usually seen as an affirmative defense. Defendants bear the burden of proving affirmative defenses.
“Innocent until proven guilty” refers to the prima facie case—the basic elements of the crime that the prosecutor must prove beyond a reasonable doubt in order to justify a conviction. For example, the elements of the crime of robbery at common law are: (1) the taking of the property of another (2) from his or her person or in their presence (3) by violence, intimidation or threat (4) with the intent to deprive them of it permanently.
The prosecutor carries the burden to prove each of those elements beyond a reasonable doubt.
But affirmative defenses are basically saying “Yeah, even if all of those elements are met, there are additional facts that, if true, excuse my actions and make me not guilty of the crime.” In the robbery example, for instance, a criminal defendant could raise the affirmative defense of “Yes, I took the property of that guy, right from his hands, and I broke four of his fingers doing it, and I sure as heck was not going to ever give it back. The property was a gun that the guy was pointing at my wife and my actions were necessary to protect me and my family from threat of death or imminent bodily harm and were proportionate to the threat.”
Putting the burden on the prosecutor in this case is weird from a traditional criminal law perspective because it forces the prosecutor to prove a negative — that the accused did not act in self defense.
Notably, however, many states define manslaughter as the “unjustified” killing of another, without intent. By requiring the prosecutor to prove the killing was “unjustified” seems to place the burden on the prosecutor of proving a lack of self defense anyway.
Interesting. Thanks for the post. A man must know his limits; after reading that, I know now I would not have made a good lawyer.