From Wikipedia:
In Florida, stand-your-ground law states that an individual has no duty to retreat from any place they have lawful right to be and may use any level of force, including lethal, if they reasonably believe they face an imminent and immediate threat of serious bodily harm or death.
Martin had the right to use force in this situation.
He would have a huge burden to get that.
Apparently not. Look what Zimmerman got away with.