If Trayvon knocked him down, he was not standing...so how could he invoke a “stand your ground” defense?
Stand your Ground is just part of a larger self defense law in FL. For this case, the important part isn't the Stand your Ground part. There are 2 parts of this law relevant to this case:
1) In the SYG hearing a judge makes the decision and George only needs to prove by the preponderance of the evidence (a much easier standard to fulfill) that George acted in self defense. It throws out all state criminal charges before a jury even hears the evidence.
2) If George is successful at this point, then there can be no civil actions against him. Remember OJ? He was ruled “not guilty” but still had to pay civil damages. If, on the other hand, George is ruled not guilty after a trial, then the vultures can come out and go after his assets (probably meager) but also the assets of the homeowners assoc. and even the city of Sanford.
Of course, the feds could also (and probably will) go after George. I think it is significant that the probable cause affidavit said that George muttered “fu..ing punks” instead of “fu..ing c..ns” It makes it much harder for the feds to claim racial animus on George's part.