Fortunately, as I figured, this isn't the case. See my above post with links to information on "affirmative defense." If you admit to the killing, you have to PROVE that the justifying circumstances you're claiming actually occurred. Georgie-Boy has to go to court and prove that Trayvon aggressively attacked him, and even then he's going to have to answer for his own actions, including getting out of his car and chasing the boy while having a visible firearm, and explain why, in reality Trayvon isn't the one who was actually justified in attacking him.
It really looks like our little child-killer is in VERY hot-water, as are the police who were negligent and ignorant enough in their duties to let him go without investigation or arrest.
This case is likely to be very interesting, but like the OJ case, it will be interesting in ways that most folks aren't talking about.
The question before the jury in the Simpson case was what to do when the cops frame a guilty man. The jury decided, as I probably would have, that they had to acquit.
Personally, I find Zimmerman's account difficult to believe because it doesn't make sense to me that Martin would get into a shouting match with Zimmerman, but not a fist fight, then as Z was heading back to his truck, go jump on him then. And Z's injuries indicate a face-to-face confrontation.
So I think the jury is likely to have to decide if you can stalk someone who is not doing anything illegal or dangerous, confront them, get into a shouting match, have it escalate into a fist fight, and then if you start getting the worst of it, shoot someone to death.
Sounds like a bad precedent, because then what's to stop any bully from mixing it up with whoever they please? If they can beat up their victim, then they've won the fight... if they start losing, they can kill the guy.
If it does turn out that this is the crux of the case, I see Zimmerman going to jail for manslaughter... maybe 60 months?