<--- *avatar cough*
In the Ace Attorney games, your character, as an attorney, is obviously never violent, so they're not going to kill anyone. All the cases involve at least one murder, but your character doesn't kill, of course. In fact, it is implied that the sentence for these murders is death, so in the Phoenix Wright and Apollo Justice games, by defending your client you are actively preventing needless death. And in the Edgeworth game, you spend just as much time proving other suspects innocent as you do proving the guilt of the real perpetrator.