Zimm may not have feared for his life but understood the possibility of severe concussion and long term brain damage.
Zimmerman, knowing that he (himself) was armed, knew that if he lost consciousness, his attacker could then take his pistol and kill him with it. That would be a reason to fear for your life, in addition to having your head bashed on the concrete.
The state has an obligation to reveal ALL exculpatory evidence.
period.
If his head was bloody and been bashed in the concreate then there will be blood (with DNA) on the concrete. That is testable. Provable. Exculpatory.
If it was ignored or destroyed then there is a spoiliation of evidence and a serious nifong matter for this state wide prosecutor.
This is why stand your ground was created, to protect citizens from crack pot prosecutors.