I'd be more worried about the reverse, actually. That the jury would convict him despite the case not being fully proven. With the media circus this has become, I doubt this guy can get a fair trial ANYWHERE at this point.
There's something like 20 million people in Florida, I'm sure they can get a jury to hear the case. Casey Anthony won her case after a media firestorm after all. And yeah, juries convicting too easily is a major problem in the US.
By the way, I don't think it's enough for a defense legally even if Zimmerman honestly believed Trayvon was about to pull a gun on him. The belief has to be reasonable too. It'd be really hard or impossible for the prosecution to prove Zimmerman's subjective beliefs, but it is far easier to show that that belief was unreasonable.
There was a case back in the 80s, where a white man shot 4 black teens on the NYC subway and later claimed self-defense. The jury acquitted, much to the despair of many people who said the jury was reasoning, "it is reasonable to expect that a black man on the subway will attack you." The defendant's case there was stronger because he was not the one to initiate contact, however.
Also, doctrine is law. Law is statutes + precedent. Doesn't need to imply any illegal action. For example, is the 21st Amendment (repealing Prohibition) law?
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your 7 time champion, Link.