Dueling mothers vouch for sons at Zimmerman murder trial SANFORD, Florida (Reuters) - The mothers of Trayvon Martin and George Zimmerman told jurors in a Florida courtroom on Friday that they both recognized the screams for help heard moments before Zimmerman shot and killed Martin as coming from their respective sons. The dueling accounts came as Seminole County Judge Debra Nelson denied a defense request to throw out the highly publicized second-degree murder case against Zimmerman. She ruled that the jury should decide whether to convict the neighborhood watch volunteer, who contends that he killed unarmed black teenager in self-defense. Zimmerman's defense lawyer had asked for the dismissal once prosecutors rested their "so-called case in chief," arguing that prosecutors had failed to prove a case based "at least 98 percent (on) circumstantial evidence." Prosecutors countered that Zimmerman offered at least three different explanations for how his confrontation with Martin began, however, casting doubt on his claim of self-defense. Police initially declined to arrest Zimmerman, believing his claim of self-defense. But that ignited protests and cries of injustice in Sanford and major cities across the United States, as the case came to reflect what many see as unequal treatment of African Americans before the law. A special prosecutor later brought the charge of second-degree murder, after Zimmerman walked free following the killing for 45 days. Early on Friday, Martin's mother, Sybrina Fulton, testified that she "absolutely" recognized the voice of her son screaming in the background of an emergency call made to police moments before he died. But the defense later called Zimmerman's mother, Peruvian-born Gladys Zimmerman, as its first witness and she too said it was her son crying for help. Asked by lead defense attorney Mark O'Mara how she could be certain, she responded, "because he's my son." Testimony from voice-recognition experts has been ruled inadmissible in the trial on the grounds that it was impossible to tell from the brief, poor-quality recording whether it was Martin or Zimmerman. Testimony from the mothers certainly seem to underscore reasonable doubt about whose voice really cried out for help on the 911 police emergency tape. But it could also prompt the six women jurors to make a Solomonic decision about which mother appears to be lying. If the bone-chilling screams came from Martin, as his older brother also testified on Friday, the slain 17-year-old could hardly be the aggressor who Zimmerman claims he could only fight off with a hollow point bullet from his 9mm handgun. O'Mara, in a rare moment of neutrality outside the courtroom, told reporters that both mothers may believe they hear their sons screaming on the 911 emergency tape from police. "We have to treat them as the grieving parents they are in different ways," he said. In other testimony on Friday, prosecutors called Shiping Bao, the central Florida medical examiner who performed the autopsy on Martin. Bao said Martin did not die instantly, even though the lone bullet from Zimmerman's semi-automatic handgun pierced the right ventricle of his heart.