Zimmerman Injuries 'Insignificant', Court Hears

George Zimmerman need not have feared for his life before he shot and killed unnarmed teenager Trayvon Martin as his injuries were "insignificant", a medical examiner has said.

Valerie Rao said she reviewed Zimmerman's medical records and the pictures of his injuries taken at a police station after the confrontation in a gated community in Sanford, Florida.

"They were not life-threatening. They were very insignificant," she told the jury.

Zimmerman, 29, claimed he shot Trayvon in self-defence after the 17-year-old punched him in the face and repeatedly slammed his head into the pavement.

Ms Rao said Zimmerman's injuries were consistent with one blow to the face and one impact with the concrete.

Earlier, judge Debra Nelson told the jury to ignore comments by detective Chris Serino after he said he found Zimmerman's account of how he got into a fight with Trayvon credible.

Prosecutor Bernie de la Rionda argued the statement was improper because one witness is not allowed to give an opinion on the credibility of another.

Defence attorney Mark O'Mara had argued it was Detective Serino's job to decide whether Zimmerman was telling the truth.

But the judge agreed with Mr de la Rionda.

The prosecutor went on to question the police officer about his opinion that Zimmerman did not display any ill will or spite to Trayvon.

Prosecutors must prove there was ill will, spite or a depraved mind by the defendant to get a second-degree murder conviction.

Mr de la Rionda then played back Zimmerman's call to police to report the teen walking through his gated community in which the neighbourhood watch volunteer uses an expletive and refers to "punks".

The detective conceded that Zimmerman's choice of words could be interpreted as being spiteful.

The prosecutor also challenged Mr Serino's contention that Zimmerman's story did not have any major inconsistencies.

Zimmerman claimed he spread out the teen's arms after he shot him. But a photo taken immediately after the shooting shows Trayvon's arms under his body.

"Is that inconsistent with the defendant's statement he spread the arms out?" Mr de la Rionda asked.

"That position, yes it is," Mr Serino said, though he later noted that Zimmerman's description was consistent with the medical examiner's report.

Also on Tuesday, the prosecution called Mark Osterman, a federal air marshal who described Zimmerman as "the best friend I've ever had".

He testified that he spoke with Zimmerman both the night of and the day after the shooting.

Mr Osterman later wrote a book about his recollections of what Zimmerman told him.

Under questioning by Mr de la Rionda, Mr Osterman said that Zimmerman told him Trayvon had grabbed his gun during their struggle, but that Zimmerman was able to pull it away.

That account is different from what Zimmerman told investigators in multiple interviews when he only said it appeared Trayvon was reaching for his gun prior to the shooting. He never told police the teen grabbed it.

"I thought he had said he grabbed the gun," Mr Osterman said. "I believe he said he grabbed the gun."