In fact Zimmerman waived the "stand your ground" defense early on.<quoted text>
This case is not "stand your ground". "Stand your ground" means, at the instant of the killing, you had an opportunity to safely escape and chose not to. Since Zimmerman claims he was on the ground with Martin on top of him, there was no opportunity to escape at the instant of the killing, so it wasn't "stand your ground".
Chucky is kinda slow though.