Re: The Joker's background?
We can analyze the character and speculate but it's irrelevant. The only way we could ever get answers would be to ask Christopher Nolan himself and I doubt he ever sat down and actually wrote down an official untold background story. Everything we guess is just made up stuff because the Joker's origin or transformation doesn't exist. He just appears as a mysterious clown-like psychopath in Gotham. That's how it goes in this movie.
"I'm not in this business to protect the rules, I serve justice"