Audio experts differ on whether shouts for help on 911 calls are those of defendant George Zimmerman or of his shooting victim, 17-year-old Trayvon Martin.
One New Jersey-based expert said the screams came from Martin, while a Florida-based audio expert said the shouts were a mix of Martin and Zimmerman.
Attorneys prosecuting Zimmerman on a charge of second-degree murder hired the audio experts to compare samples of Zimmerman's and Martin's voices.
Shouts can be heard on the 911 calls phoned in by neighbors.
The residents of the gated community heard the neighborhood watch leader struggling with Trayvon Martin before he killed the teenager in 2012.
Determining whose voice was in fact calling for help could aid a jury in deciding whether George Zimmerman's claims of self-defense were justified.
Zimmerman is pleading not guilty and his trial starts next month.
Martin's family claims the voice is that of the South Florida teen, while Zimmerman's father has said in court he believes the cries are from his son.
Zimmerman's attorney, Mark O'Mara, asked a judge to determine whether the audio analysis can be used at trial, or whether it would prejudice jurors.
"Counsel has significant concerns that such evidence will confuse the issues for this jury to decide, and it may well mislead the jury in this area of inquiry," he said.