I think the lawyer indicated that Martin's actions were legitimate even under standard self-defense doctrine. This leaves Stand Your Ground as a backup.
Since he was patrolling the neighborhood, I don't think it applies:
"(a) The person against whom the defensive force was used was in the process of unlawfully and forcefully entering, or had unlawfully and forcibly entered, a dwelling, residence, or occupied vehicle, or if that person had removed or was attempting to remove another against that persons will from the dwelling, residence, or occupied vehicle; and..."
http://www.leg.state.fl.us/statutes/index.cfm?App_mode=Display_Statute&Search_String=&URL=0700-0799/0776/Sections/0776.013.html