A defendant charged with a crime who wants to raise Stand your Ground files a motion to dismiss claiming stand your ground immunizes him from prosecution....
A hearing is held before trial. The burden is on the defendant to prove by a preponderance of evidence that stand your ground immunity applies.Merritt is discussing a decision by a Florida judge she respects who denied an immunity motion and explained how different the burden of proof is at trial. That case was not the one involving George Zimmerman and Trayvon Martin, but it explains the way the Stand Your Ground law does have some application to Zimmerman, even though the facts in Zimmerman's case don't seem to involve whether or not there is a duty to retreat.
The judge weighs the facts. If the judge agrees the defendant has shown stand your ground immunity applies by a preponderance of evidence, the charges are dismissed. The defendant can't be prosecuted.
If the judge finds the defendant hasn't met his burden, (including if the disputed evidence is so equal on both sides the judge can't decide one way or the other) the case goes to trial to be decided by the jury. At trial, the defendant can still argue both self-defense and stand your ground immunity -- he only has to establish some evidence of his theory, which can be just his own testimony, that he acted in self-defense.
The prosecution must prove his guilt at the jury trial beyond a reasonable doubt. Which means, if the defendant raises self-defense or stand your ground at trial and gets the jury instruction, the state, which has the burden of proving guilt beyond a reasonable doubt, must disprove self-defense. If the jury has a doubt, the defendant must be acquitted.
That is, there is a pretrial motion to be made, with a judge making the decision about the evidence and a preponderance burden of proof on the defendant. The defendant can win at that point or be sent on to trial, where the prosecution will have the burden, even the burden to disprove self-defense, and the standard of proof is beyond a reasonable doubt, much higher than what the defendant would have had to prove to avoid the trial.
So, to put it somewhat crudely — and please correct me if I'm wrong — assume, hypothetically, that any factfinder will decide there's only, at most, an equal chance that it was self-defense, but there's some reasonable likelihood. The judge as factfinder at the immunity motion phase must deny the motion, but the jury as factfinder after the trial phase must acquit.