[DanielDudley]

You want to show that nobody wanted this to happen, and nobody had it coming.

This of course implies that some people do in fact have it coming. Some do, and that can be part of a defense. It seems to me that it goes both ways.

Is it worse if you rape and kill someone's daughter than it is if you kill someone who raped your daughter ? I would say yes, and that sometimes it is important to let people know that the person who was killed was either a scumbag or a saint. Should it influence sentencing? Perhaps it should. I would want a rapist and a killer to be put to death, or whatever the worst possible punishment was. I would want you to receive the very lightest sentence if you took the life of someone who did something heinous and you took action in response. Justice is more than just guilt or innocence. That is why we have juries.