Whether trained or untrained, most cops aren't actually that big a fan of killing other human beings. Crazy claim, I know. Combined with your graph, I'd say the it appears as though there is no correlation and it's easily explained why that is the case. Training isn't going to magically make cops not shoot people, and this is just my hypothesis/theory but if there's a situation where there is serious danger requiring drawing your weapon, you're usually past the point of deescalating the situation, which is what more training would mainly help you get better at. So I can imagine it wouldn't make the biggest difference in fatal police shootings. In fact, more training = more gun training so I suppose cops would be more accurate, and cops always go for the torso, not legs to immobilize the target safely, like some idiots think they do.