http://news.yahoo.com/why-trayvon-martins-killer-isnt-under-arrest-3-112200073.html
"The 2005 law allows permitted gun owners like Zimmerman to use lethal force on anybody, in any public space, if they reasonably believe it will "prevent imminent death or great bodily harm." Courts say the burden is on prosecutors to prove that the shooter was not acting in self-defense, so "some Orlando-area police agencies simply stopped investigating shootings involving self-defense claims," says Henry Pierson Curtis in the Orlando Sentinel. "In case after case during the past six years, Floridians who shot and killed unarmed opponents have not been prosecuted."'