But John Good told the jury in the Seminole County trial Friday he did not see Martin pounding Zimmerman's head on the pavement.
First responders testified they noted Zimmerman's clothing was wet and he had contusions and lacerations on his head, the Orlando Sentinel reported. Officer Tim Smith also said Zimmerman looked confused.
Zimmerman, a neighborhood watch volunteer in the gated community where Martin was staying with a relative, is charged with second-degree murder. Prosecutors say he followed Martin, 17, initiating the confrontation that led to the shooting.
Defense lawyers say Zimmerman fired in self-defense after Martin attacked him.
Another neighbor, Jonathan Manalo, said he arrived on the scene after the shooting and watched as police handcuffed Zimmerman. He said he used his cell phone to photograph Zimmerman's injuries and Martin's body and, at Zimmerman's request, called his wife.
"Just tell her I shot someone," Manalo said Zimmerman told him.