A person has shot and killed or wounded another in a public place. The shooter is at the scene.
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There's no camera footage to review, and either person could be the "good guy". So we (actually, arriving officers, probably supported by detectives) try to piece together what happened. One thing is certain: that the shooter may be a "gun guy" who had a clean record at the time he received his CHL does not automatically make the incident a likely case of a justified shooting, regardless of what some of us might like to think.
So--here's the shooter's account: two men stepped up to him from behind, one with his hand in a pocket, demanded his wallet, and threatened to kill him. Due to the disparity of force, the closeness of the men, the verbal threat, the likelihood that one had a weapon, and the fact that his car prevented him from evading or escaping, he had to draw and fire. One was hit, the other dropped a knife and ran off.
Now, the account of the wounded man and his accomplice: We stopped for a moment to light a cigarette, and a man shot us without warning and for no reason.
The testimony of the one witness who came forward: I was unlocking my car and I heard three shots. I turned and saw that man holding a gun, and another man on the ground. The shooter was standing there (when I first saw him), which contradicts the shooter's account of where he had been standing when he fired.
The forensic evidence shows that actor's gun was used in shooting the victim, and GSR shows that the actor had fired a gun, as he said. There is no GSR on the victim. No other weapon was found at the scene.
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To get a better idea, one might need to have (1) the account of that other witness who drove off, never to be found, while the shooter was saying that he would not say anything; (2) or that knife that was not secured at the scene, because the arriving officers had absolutely no indication that this might have been a self defense shooting, and later disappeared; or (3) just maybe, some tests of the shooter's ammunition to show whether GSR would have been expected on the victim at the distance claimed by the shooter.
And of course, other things may come to light. Perhaps the shooter has posted something like, "if anyone tries to break into my car, I'll shoot to kill! No one deprives me of my property". That, combined with his use of Black Talons, for example, might give some idea regarding the shooter's state of mind.
We ... need to understand that one's attorney has no way of producing evidence that did not exist, or that has not been made available to him or to her.
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What does this all tell us? It tells us that the old saw, "a good shoot is a good shoot" really doesn't mean very much at all unless the evidence that supports the claims of the shooter is sufficient to counter that which does not.