He said the wound indicates the gun was against the teen's clothing when Zimmerman fired but was two to four inches from his chest. 
 
"The fact that we know that the clothing was two to four inches away is consistent with someone leaning over the person doing the shooting."
 
Di Maio is a retired medical examiner now in private practice. He testified Zimmerman's head lacerations are consistent with his story that Martin pounded his head into the pavement. He said the force would have been enough to stun Zimmerman.
 
He also described how the bullet pierced Martin's heart and lung, and how the teen could have maintained consciousness 10 to 15 seconds after the gunshot. Di Maio said Martin would not have felt pain after losing consciousness.
 
Martin's mother Sybrina Fulton left the courtroom as Di Maio began his testimony. But the teen's father Tracy Martin remained, looking on without showing emotion.
 
Zimmerman says he shot and killed Martin in self-defense.