I think that you've got to look at this from the opposite perspective. Let's say that you're involved in an absolute 100% legitimate SD shooting but you do not report it.
What's going to happen when the body is found or the bad guy goes to the hospital? There's going to be an investigation, they're going to look for witnesses, security cameras, they're going to get a statement from the BG if he lives and it's NOT going to be "Yeah, I attacked this guy and he defended himself." If the guy is dead then the police have an unsolved murder on their hands. Odds are that they will eventually find you. They're not going to be happy that you didn't come forward. There WILL be a presumption of guilt. I promise you that. Innocent until proven guilty is a nice concept.... anyone remember the Duke lacrosse case?
I agree that there could be a danger of "self-incrimination" to some degree but the other side of the picture is worse. Much worse.
Still happily answering to the call-sign Peetza.
The problem, as you so eloquently put it, is choice.
He is no fool who gives what he can not keep to gain what he can not lose.
-Jim Eliott, paraphrasing Philip Henry.