The judge must decide whether prosecutors can use two expert witnesses, including Alan Reich, who testified Friday he was able to discern the 17-year-old Martin screaming, "I'm begging you," in the moments before he was shot and killed in February 2012, the Orlando (Fla.) Sentinel reported. Alan Reich is the only expert who has studied the tape to make such a clear finding.
Zimmerman, scheduled to go on trial Monday on a charge of second-degree murder, has pleaded not guilty.
Prosecutors say Zimmerman trailed Martin, who was unarmed, through a gated community in Sanford, Fla., after a 911 dispatcher advised Zimmerman to back off, and then killed him. Defense lawyers say Zimmerman acted in self-defense after Martin attacked him.
Prosecutors also say Zimmerman racially profiled Martin, who was black.
John Peter French, a British expert, told Judge Debra Nelson Saturday screams cannot be compared to a normal voice. He said he would have rejected the audiotape out of hand, and would not have analyzed it, if it had been submitted to his lab.
George Doddington, a former employee of Texas Instruments who also testified for the defense, suggested speech comparison is an uncertain area.
"Speech is not like fingerprints," he said. "Speech is not like iris scans. Speech is not like DNA."
Tom Owens, a potential prosecution witness, his analysis found Zimmerman was not the person screaming.