I don't think justifiable homicide such as self-defense should count if you're wanting to answer a question of "should we keep guns or get rid of them"

Obviously having more justifiable homicides with guns is better than gun murders, because it's good people protecting themselves from violent people. I don't think a criminal who died from trying to kill me deserves to be added to a statistic to further an idea that "less guns are better"

Speaking of Trayvon Martin, we'll never really know what went down because we can't get in those two's heads, but I can tell you if I was armed and found myself getting my face beaten into the concrete, not knowing what the person would do next, I think I'd certainly feel justified in using a projectile weapon. If somebody is beating you senseless on a dark night, I don't know about you, but I wouldn't assume they'll just leave you after you black out. They may curb stomp you to death, they may take your gun and kill you, they may take your gun and kill somebody else.