There’s a sequence involved: a charge is made, that charge is that the individual unlawfully took someone’s life, the case goes to trial, at that point the defendant claims it was self defense, and the jury decides whether the claim that he unlawfully took someone’s life is true or whether they accept his excuse.
There’s nothing to keep the defendant from claiming it was self defense to the police, but that has no impact if the prosecutor decides to lodge a charge.
I think your route’s circular because a case where the defendant claimed self defense wouldn’t be a crime under your construct. How would false claims of self defense be adjudicated if just saying it was self defense makes it a non-crime?
So basically if there’s an unnatural death they have to call it an unlawful death and if they have reason to believe that a specific person was involved in causing the death they have to charge them with a crime? Only after charging somebody with a crime can they give the person the opportunity to explain that it was self-defense, it was an accident, etc?
If that’s the case then Zimmerman should have been arrested a long time ago.
I think the only non-circular route is to have the evidence regarding whether a crime was committed determine whether it was an unlawful death.
For instance, suppose somebody was observed suddenly keeling over dead on the sidewalk, with an appearance consistent with poisoning, or overdose maybe. At what point would they consider it an “unlawful death”?