George Zimmerman's wife and father told a court on Friday he was a non-violent person and they would help ensure he does not flee should he be released on bail for a second-degree murder charge in the death of black Florida teenager Trayvon Martin.

I've never known him to be violent at all, unless he was provoked, and then he would turn the other cheek, father Robert Zimmerman testified under defence questioning at a Florida court.

Zimmerman's lawyer Mark O'Mara was attempting to get his client released on bail in a case that has captivated the United States and prompted civil rights demonstrations around the country.

Zimmerman, 28, shot and killed the unarmed Martin, 17, in what he said was self-defence following a confrontation in a gated community in the central Florida city of Sanford on February 26.

Police initially declined to arrest Zimmerman, citing Florida's Stand Your Ground law, which allows people to use deadly force when they believe they are in danger of getting killed or suffering great bodily harm.

Civil rights activists say racial prejudice played a role in Zimmerman's decision to view Martin with suspicion and in the police decision not to make an arrest.

A special prosecutor later assigned to the case eventually charged Zimmerman with second-degree murder and he turned himself in on April 12 when he was booked into Seminole County Jail.

At the bail hearing at Seminole County Court in Sanford, Zimmerman's relatives testified via telephone, while Martin's parents and their legal team listened from the gallery.

O'Mara surrendered Zimmerman's passport to the court to show that Zimmerman would not flee the country should he be released.

The hearing continued with O'Mara putting questions to Zimmerman's relatives, including his wife Shellie, who said she had not seen her husband since he went into hiding shortly after the February 26 shooting.

Prosecutors asked them if they were aware of his arrest in 2005 for assaulting an alcoholic beverage control agent in an attempt to demonstrate Zimmerman had a violent past. Zimmerman avoided jail time then by attending an anger-management course.

O'Mara also questioned Zimmerman's father Robert and mother Gladys while Zimmerman listened silently, clean-shaven and wearing a dark suit with a light shirt and silver tie.

Zimmerman, the son of a white father and a Peruvian mother, had been in hiding for more than six weeks between the shooting and turning himself in.

Thousands of people had demonstrated in rallies in Sanford and around the nation to demand his arrest and criticize the police.

Zimmerman's relatives and supporters deny he is racist and say has been unfairly vilified. They say he feared for his life during his altercation with Martin and was justified in using deadly force.

According to 911 recordings, Zimmerman called police on the night of February 26 to report what he called a real suspicious guy, then followed Martin against the advice of a police operator.

Zimmerman told police he was walking back to his truck when Martin attacked him, flooring him with one punch to the nose. Martin then repeatedly slammed Zimmerman's head against a concrete walkway, Zimmerman's brother and father have said. Zimmerman then pulled out a 9mm handgun he was licensed to carry and shot Martin once in the chest.

(Reporting by Tom Brown, Barbara Liston and Chris Francescani; Editing by Daniel Trotta and David Brunnstrom)