There's also the matter of chamber of Zimmerman's gun being empty, which raises the possibility that he may have been shot during a struggle for posession of the gun.
I assume they also have, or will have the lab work on Trayvon's blood chemistry which may yield some evidence.
Not relative to the case, just curious:
Wonder if Tracy Martin has any DUI or PI charges? Many young people involved in the things Tray seemed to be interested in are simply doing their own interpretation of a parents behavior.