A U.S. judge said Friday he won't immediately rule on bond for the neighbourhood watch volunteer who killed unarmed black teen Trayvon Martin. That means George Zimmerman remains in jail in a case that set off national protests over race and self-defence laws.

The judge did not indicate when he might make a decision.

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Sybrina Fulton (left) mother of Trayvon Martin and attorney Benjamin Crump, arrive at the Seminole County Criminal Justice Center to attend a bond hearing for George Zimmerman on Friday. (John Raoux/Associated Press)

Zimmerman's $150,000 bond was revoked earlier this month when prosecutors told the judge he and his wife misled the court about how much money they had. Prosecutors said a website Zimmerman created for his legal defence had raised $135,000 at the time of his first bond hearing, and Zimmerman and his wife did not mention the money then. Zimmerman's wife, Shellie, has been charged with perjury.

Zimmerman has been charged with second-degree murder in the 17-year-old Martin's death during a dispute after a suspicious Zimmerman followed Martin through a gated community. The 44 days between the shooting and Zimmerman's arrest inspired nationwide protests.

Zimmerman has pleaded not guilty and claims the shooting was self-defence under the state's "stand your ground" law.

Hearing seemed like a trial

Martin's parents and supporters say the teenager was targeted because he was black and Zimmerman started the confrontation.

Zimmerman's father is white and his mother is Hispanic.

At times, Friday's hearing had the flavour of a trial, with both sides presenting what sounded like opening statements. But the judge stayed focused on the bond issue.

Zimmerman's attorney has argued in court papers that his client is no threat to the public and proved he wasn't a flight risk by returning to jail when his earlier bond was revoked.

The attorney on Friday tried to show there was no effort to hide the money from the judge.

"It is not the grand conspiracy the state seems to suggest," attorney Mark O'Mara said.