This may help PoweRob.
Criminal Law: Defenses FAQs - Lawyers.com
I am not wrong on this.The defense of "self defense" is what's called an "affirmative defense." The prosecution must disprove self-defense beyond a reasonable doubt.
You can read more
Self Defence - Defence to criminal charges
Defending the Self-Defense Case
The best case I think, based on all of the evidence we have, for the prosecution to score a conviction is to prove the Zimmerman used excessive force in defending himself. They cannot (based on what we know) prove that he was not acting in self defense. But they may be able to prove that lethal was not needed.
This is an excellent development. The persecution of George Zimmerman should come to an end. As citizens, we need to preserve our right to self-defense. The race of the decedent attacker ought to be irrelevant, however as Ric astutely points out, the NAACP, Jesse Jackson, and Al Sharpton exist to perpetuate racism and foment ethno warfare.
The standard action taken for self defense cases is the concept of an affirmative defense. The accused agrees to part of the charge (the actual killing), but puts for evidence to justify their actions. Exactly what standard of proof is required is quite variable depending on jurisdiction and circumstances.
For a decent legal analysis of Florida's stand your ground law an its application to the Martin case.
Florida's Stand Your Ground Law : Use of Deadly Force in Self-Defense
In summary, based on other cases involving the same law, the defense can file a motion for immunity in a pre-trial hearing. For the motion to succeed, the defense must meet the standard for "preponderance of the evidence". Barring such a ruling, the case moves to trial as usual.
Under SYG as it has been interpreted by the courts in Florida. The burden of proof rwmains entirely on the prosecution if the defendant simply RAISES or CLAIMS self defense.
All one needs to do is claim they killed in self defense and it becomes necessary to prove beyond a reasonable doubt that they WEREN'T acting in self defense.
Another affirmative defense is insanity. You killed but were crazy at the time so aren't responsible. YOU are required to prove you're crazy.
So if there was an insanity version of SYG, you would simply have to claim you were crazy and the prosecution would have to prove you WEREN'T.
Anyone wondering what I'm talking about start here:
The Psychology of Persuasion