ORLANDO, Fla. -- The former neighbourhood watch volunteer charged with killing an unarmed black U.S. teen asked for a new judge again Friday, saying the current one is biased because he said George Zimmerman had "flaunted the system."

Zimmerman is charged with second-degree murder in the shooting of Trayvon Martin, a case that raised questions about race and self-defence laws. He has pleaded not guilty and is out on bail.

Zimmerman said in a motion he feared he would be unable to get a fair trial with Circuit Judge Kenneth Lester. Lester was appointed in April after Zimmerman claimed a potential conflict of interest with the original judge.

Earlier this month, Lester said in an order granting Zimmerman bond that Zimmerman had "flaunted the system" by failing to disclose at an April bond hearing that he had raised $135,000 from donations for his legal defence.

Lester at the time allowed Zimmerman to be released on a $150,000 bond, but he revoked the bond after prosecutors presented jailhouse recordings of Zimmerman instructing his wife on how to transfer funds raised from a website to different bank accounts.

Zimmerman returned to jail in June but left last week after Lester granted him a $1 million bond, saying state law compelled him to grant bail.

A spokeswoman for the judge said he wouldn't comment Friday.