ORLANDO, Florida (AP) — Forensic tests made public today show that George Zimmerman's was the only DNA that could be identified on the grip of the gun used to fatally shoot 17-year-old Trayvon Martin.

The results rule out Martin's DNA from being on the gun's grip. Zimmerman's DNA also was identified on the gun's holster, but no determination could be made as to whether Martin's DNA was on the gun's holster, according to the report from the Florida Department of Law Enforcement.

Zimmerman is charged with second-degree murder for fatally shooting Martin during a confrontation in a gated community in Sanford in February. Zimmerman is pleading not guilty, claiming self-defence.

A delay in Zimmerman's arrest led to nationwide protests.

The question of whose DNA is on the gun and holster could play a role in Zimmerman's defence.

Zimmerman said Martin had been on top of him, slamming his head against the ground and smothering his mouth and nose with his hand and arm when he grabbed his gun from a holster on his waist before Martin could get it. He shot the teenager once in the chest.

Other documents released by prosecutors include an interview with the clerk of a convenience store where Martin purchased Skittles and a can of iced tea moments before his confrontation with Zimmerman. The clerk said in the interview, more than a month after Martin was shot, that he didn't remember Martin.

"To be honest, I don't even remember that day," said the clerk, whose name was redacted from the audio interview.

Prosecutors also released hundreds of emails sent to then-Sanford Police Chief Bill Lee whose agency came under fire when Zimmerman wasn't immediately arrested. An email dated more than a week after Martin's death from a resident of the development where Zimmerman was the neighbourhood watch leader thanked Lee for attending a recent association meeting. The email's author, Molly Jackson, said in an interview Wednesday that Zimmerman wasn't present at that association meeting.