Volokh Channeling McKinnon/Dworkin?Professor Volokh points to this article about a woman in Texas arrested after shooting to death her estranged husband. It appears to have been an act of self-defense, as the dead guy had broken into the woman's home the night before she was to go to court and seek a restraining order against him. Volokh thinks that this arrest violated the Fourth Amendment, because the police did not have probable cause to believe a crime had been committed. I think this argument fails, for theoretical and practical reasons. First, self-defense as a justification for homicide is an affirmative defense, on which the defendant bears the burden of proof. That, at least is the law in Illinois. See 720 ILCS 5/7-1 & 7-14. I haven't done a 50-state survey, but I'd be willing to bet that's the case most everywhere, and has been since time immemorial. In other words, homicides are presumptively crimes at the arrest stage, and a peace officer has probable cause to arrest if he has probable cause to believe there has been a homicide (as opposed, say, to an accident). If I had any free Westlaw time this month (I don't), I'm sure I could dig out a case or 6 that so hold.
And practical considerations militate against asking a peace officer to make these fact intensive determinations on the spot. Just one hypo: a gang member finds himself alone in the territory of a rival gang, and is shot dead. Police arrive, finding only members of the shooter's gang, all of whom swear up and down to the officer that the dead man was threatening and the shooting was done in self-defense. What result? Or simply take the Texas case. The dead man looks like a bad guy. But is it possible he just went there to talk? Not likely, I'll admit. But it is possible, and if it's true then the wife (BWS aside) is a murderer. He apparently has a record of beating the woman; but do we expect every cop to know such background when called to the scene of a shooting? I think the answer is obvious. I appreciate Professor Volokh's principled views on the Second Amendment (though I don't share them). I think on this question, his zeal for that cause has led him astray.