Brentos said:
That doesn't apply to rules of a game
Why are a character's in-game thoughts any less real than a character's in-game acts? They're both fictional. And as per previous discussion on this thread, thoughts and beliefs are integrated into the alignment rules, so if you consider alignment a rule, thoughts do apply.
Brentos said:
As far as the game rules go, the DM *is* the universe, or at least all relevant aspects of it that act in the game.
I think you're conflating DM as person with DM as world-creator. The DM knows everything about the universe that he could know, but assuming the universe itself can know things omnisciently, there are things the universe could know that the DM could not (the true motivation of a character, for example).
After all, the DM controls 99.999% of the universe, but there's one thing he doesn't control: the PCs.
Brentos said:
As far as the game goes, he is still evil. Now, if the DM and player want to skip the game ahead for 30 years for the sake of drama and change alignment, that is cool! The player still needs to prove it, though.
But for the 20 years in prison, that character has performed no evil acts. Not killing is at least neutral, I would think. If you're saying he's still evil, that can only be based on motivation and intent, because he would be killing if he could, but he can't. His actions are neutral while in prison.
If actions are all that matters, this guy is neutral. He hasn't killed a halfling (or anyone else, presumably) in 20 years. If motivations matter, he's still evil, because he intends to kill halflings as soon as he gets the chance.