(SANFORD, Fla.) -- Trayvon Martin's mother, Sybrina Fulton, and his older brother took the stand on Friday to tell jurors in the George Zimmerman trial that the voice screaming for help on the 911 calls was that of the slain Florida teenager.
"That scream, do you recognize that?" prosecutor Bernie de la Rionda asked Martin's mother.
"Yes, it's Trayvon Benjamin Martin," she answered.
Zimmerman, 29, faces second degree murder charges for Martin's death. He maintains he shot the unarmed teenager in self-defense after he was confronted and attacked by Martin, 17, on Feb. 26, 2012. Prosecutors allege the former neighborhood watch captain profiled, followed and then shot Martin as he was walking back to the residence where he was staying as a guest.
Prosecutors hoped that the testimony of Martin's mother and brother would have an emotional and convincing impact on the jury and that the jurors would tie their 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.
Nakaosone said, however, the best person to identify the voice would be someone who is intimately familiar with the voice.
During cross examination, defense attorney Mark O'Mara asked Fulton if she hoped it would be her son, because if it wasn't that could mean Martin was responsible for his death, O'Mara said.
"I heard my son screaming," Fulton replied. "I didn't hope for anything. I simply listened to the tape."
It's not clear what impact it could have the jury, which consists of six women.
A major point of contention in the trial is who was heard screaming for help in the background of 911 tapes the night Martin was killed. Zimmerman's father insists that it is his son's voice that is heard.
Moments before she began her testimony, Fulton tweeted, "I pray that God gives me strength to properly represent my Angel Trayvon. He may not be perfect but he's mine. I plead the blood of Jesus for healing."
Martin's brother, Jahvaris Fulton, also told the jury that the voice on the tape was that of his brother.
But under cross examination, O'Mara played a tape of an interview with Jahvaris in which Jahvaris is heard saying "I'm not sure" when asked if that was his brother screaming. The jury was out of the courtroom at the time the tape was played. It's not clear whether they will be allowed to hear it at some point.
O'Mara had asked Jahvaris whether or not he had ever doubted that the screams were from his brother.
"When we heard it in the mayor's office I didn't want to believe it was him. It was clouded by shock and denial and sadness. I didn't want to believe it was him," the brother said.
Copyright 2013 ABC News Radio