"It's going to go a lot better if you've got a friendly witness who isn't a stranger in town, or the perpetrator is known to the guards as a not-well-connected criminal.  In your case, given your total absence of papers, I'd say that the law on self-defense is to kill them while there aren't any witnesses... is that okay with your Lawful thing?"

"It's going to go a lot better if you've got a friendly witness who isn't a stranger in town, or the perpetrator is known to the guards as a not-well-connected criminal.  In your case, given your total absence of papers, I'd say that the law on self-defense is to kill them while there aren't any witnesses and get me to help hide the body... is that okay with your Lawful thing?"