There isn't always a clear-cut sense of "right" and "wrong" within the happenings of a criminal investigation or its ensuing trial. Very often, someone will have to make a judgment call that won't be viewed favorably by everyone else, but the person making the call is doing it for what they believe to be a noble reason. Jack McCoy was faced with such a call in the trial at the center of the episode "Red Ball," where the only way to know where a kidnapped girl is located is to cut a deal with a criminal.
A man named Dwight Jacobs ends up inadvertently kidnapping the girl when he carjacks her mother's car, and, after being arrested, refuses to reveal the girl's location unless he is let go. McCoy ends up secretly making that deal without alerting the DA's office, and the girl is found unharmed. However, when the judge catches wind of the backdoor deal, he refuses to accept it and instead charges Jacobs the maximum kidnapping sentence. Angry over the whole ordeal and the way McCoy went about it in secret, DA Arthur Branch (Fred Thompson) tells McCoy that he'd never be the DA. Of course, McCoy replaced him in the very next season.
