>> if he had a free hand to reach for his gun, why didn’t he use that hand to fight off his “attacker”?
Hmmm... someone is attacking you, in a manner that causes you to fear that he intends to take your life.
You decide you must defend yourself, and you have two weapons at your disposal — in Z’s case, a fist and a gun.
I was not aware that there is anything in self defense law that specifies which of your available weapons you may use to defend yourself, and which you may not use. In other words, I don’t think you’re obligated to calculate just how *little* force you must apply to succeed. Can you find me a reference?
(And that leaves aside the whole question of whether or not Z’s fist *would have been* adequate defense. Actually, the defense effectively argued, using witnesses, that Z was probably not capable of fighting off St. Trayvon with his hands.)
That's the statutory language for justified use of force. I notice your hypothetical is premised on fear of death. Reasonably (the jury decides) holding a fear of death is a prerequisite for resort to deadly force. The firing of a firearm in the direction of "the person to be arrested" (read that as "stopped") is always deadly force, see 776.06.
In situations that do NOT involve a reasonable fear of death or serious injury, self defense force MUST be measured. If you are ambitious, look up the jury instructions for additional detail.