By Barbara Liston
SANFORD, Florida (Reuters) - The presiding judge in the George Zimmerman trial was expected to rule Friday on the admissibility of testimony from audio experts for the prosecution which suggested that unarmed black teenager Trayvon Martin screamed for help before he was shot and killed by Zimmerman in February 2012.
The ruling from Circuit Judge Debra Nelson in Florida's Seminole County is the last major hurdle before opening statements in the high-profile trial are set to be heard on Monday.
Jury selection in a case that has drawn groups protesting what they saw as racially biased law enforcement practices, ended on Thursday with the unusual selection of a six-member all-female panel.
The protests were sparked by the fact that Zimmerman was not initially arrested in the killing of 17-year-old Martin, and remained free for 44 days, after claiming self-defense in the shooting.
Two state experts, in what they qualify as tentative or probable findings because of the poor quality of the recording, have said that the chilling screams heard in the background of a 911 call moments before the fatal shooting came from Martin.
Lawyers for Zimmerman, a former neighborhood watch volunteer, have sought to block the testimony on grounds that the methods used by the state's voice recognition experts are based on questionable science.
They acknowledge, however, that the testimony could play a huge role in swaying the jury. "This is perhaps the most important evidence in the case," defense lawyer Don West told the judge.
Audio experts testified for the defense in a lengthy pre-trial hearing arguing that voice recognition techniques cannot identify an individual from screams made under extreme duress. An FBI expert retrieved less than three seconds of screaming unobstructed by talking on the 911 call. But that was not enough, by FBI standards, to attempt an identification.
On Friday Judge Nelson also dismissed a defense motion to bar certain words and phrases from the prosecution's opening statement. She ruled prosecutors could allege that Zimmerman, who is Hispanic, "profiled" Martin but ordered them not to use the term "racial profiling."
Defense lawyer Mark O'Mara objected, saying the terms "racial" and "profiling" went together "like peanut butter and jelly."
The judge also ruled that prosecutors could use the terms "vigilante" and "wannabe cop" when referring to Zimmerman, and will be allowed to say he "confronted" Martin before the dispute that ended with the younger man's death in a gated community in this central Florida town.
"That's the state's case, so they will be allowed to do that," Nelson said.
She had earlier ruled that Zimmerman's defense team, in their opening statements, would not be allowed to refer to Martin's alleged marijuana use or Facebook postings.
The panel of six women, five of whom are white and one part-Hispanic, was selected from a pool of 40 potential jurors. They will remain anonymous for the duration of the trial and have been referred to in court only by number.
"The personalities and the sensibilities of the women on this jury are much more important than their demographic characteristics," said Richard Gabriel, a trial consultant and president of California-based Decision Analysis.
"The fact that they are all women and mostly middle-aged to older may make it easier for them to get along - which favors unanimity, whether for guilt or innocence instead of a hung jury."
The jurors, backed up by four alternates, will decide whether Zimmerman, 29, is guilty of second-degree murder, a charge that carries a potential life sentence.
Zimmerman has pleaded not guilty.
(Additional reporting and writing by Tom Brown. Editing by David Adams and Gunna Dickson)