Attorneys for Zimmerman -- who has pleaded not guilty to second-degree murder in the February 2012 shooting death of Trayvon Martin -- are asking Judge Debra Nelson not to allow prosecution experts in voice and speech identification to testify regarding analysis of a recording of a 911 call on which a voice can be heard screaming for help. The defense has argued the state's analysts are employing unproven science, the Orlando Sentinel reported.
Discussion of the matter had just begun Thursday when Nelson recessed court until Friday, the newspaper said.
Nelson denied a defense motion earlier Thursday to conceal the identities of some witnesses in the trial.
Defense attorney Mark O'Mara argued important witnesses might be afraid to give testimony exonerating Zimmerman, who has invoked a self-defense claim in the slaying of Martin, an unarmed black teenager in Sanford.
Zimmerman's trial is scheduled to begin Monday with jury selection.
A letter from the American Civil Liberties Union of Florida to the chief judge of Seminole County complained about restrictions on demonstrations outside the courtroom, calling the restrictions broad and vague, the newspaper said.
Any demonstrators at the trial will be prohibited from bringing chairs, coolers and protest signs with metal or wooden handles, the letter noted.