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George Zimmerman Jury to Hear from Trayvon Martin's Mother

Gary W. Green-Pool/Getty Images(SANFORD, Fla.) -- The prosecution is expected to wrap its second-degree murder case against George Zimmerman on Friday with the mother of Trayvon Martin testifying that the person heard screaming for help on a 911 tape is her son.

Sybrina Fulton, the mother of the slain teenager, will take the stand on the ninth day of testimony in the Florida trial.

Fulton and Tracy Martin, Trayvon Martin's father, have been present every day of the trial and endured testimony about the shooting and their son's wound that at times have prompted them to abruptly leave the courtroom.

Zimmerman, 29, maintains that he shot the unarmed teenager in self-defense after he was confronted and attacked by Trayvon, 17, on Feb. 26, 2012.  Prosecutors allege that the former neighborhood watch captain profiled, followed and then shot Trayvon as he was walking back to the residence where he was staying as a guest.

Fulton's testimony could be particularly powerful for the jury of six women.

A major point of contention in the trial is who is heard screaming for help in the background of 911 tapes the night Martin was killed.  Fulton claims it is Trayvon screaming, while Zimmerman's father insists that it is his son's voice that is heard.

The prosecution hopes that Fulton's testimony will have an emotional and convincing impact on the jury and that the jurors will tie her words to the opinion of FBI audio expert Hirotaka Nakasone, who testified earlier in the trial that it was not technically possible to identify the voice.

He said, however, the best person to identify the voice would be someone who is intimately familiar with the voice.

It is unclear if Trayvon's father will also take the stand because he initially told police he doubted it was the voice of his son.

Zimmerman's father, Robert, may eventually testify for the defense.  He has been consistent that the screams for help are from George.

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