Story highlights A defense lawyer says other evidence, not the 911 call, will determine the case 
 
 A lawyer for Martin's family says he thinks the jury will find Zimmerman guilty 
 
 Gladys Zimmerman says she knows the panicked voice is that of her son 
 
 Earlier, Trayvon Martin's morther said that it her son's voice on the 911 call 
 
 Was it George Zimmerman or Trayvon Martin who screamed for help the night the 17-year-old Martin was shot dead? 
 
 That could depend on which mother the jury believes. 
 
 Both Zimmerman's and Martin's mothers expressed no hesitation Friday in separate court appearances as to whose panicked voice is heard screaming during a 911 call from that February 26, 2012, night in Sanford, Florida: Each said it was her son. 
 
 That contradiction -- with Sybrina Fulton insisting it was her son, Trayvon, who cried out, while Gladys Zimmerman said it was her son, George, who was yelling after being attacked by the teen -- was central to Friday's court proceedings, and central to the second-degree murder case unfolding in central Florida. 
 
 Zimmerman has pleaded not guilty and claimed he shot the teenager in self-defense. The 911 call played twice in court on Friday, his lawyers claim, back up their assertion that it was Martin, and not their client, who was the aggressor. 
 
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 Testifying late Friday afternoon, Gladys Zimmerman said she was sure George was the one yelling. Why? 
 
 "Because he's my son." 
 
 She answered "all of the above" when asked whether she had ever before heard her George Zimmerman laugh loudly or cry out for help. This instance, though, Gladys Zimmerman admits was different. 
 
 "I haven't heard him like that before," she said as her son wiped away tears in the courtroom. "The anguish, the way that he is screaming it describes to me anguish, fear, I would say terror." 
 
 Contrast that to the very different story offered a few hours earlier by Sybrina Fulton, who was stoic as prosecutor Bernie de la Rionda played the 911 call. 
 
 When asked whether she recognized the screaming voice, the mother -- who earlier stated that her son was "in heaven" -- said it was that of "Trayvon Benjamin Martin." 
 
 Defense attorney Mark O'Mara followed up by asking her, "As his mother, there was no doubt it was him screaming?" 
 
 She replied: "Absolutely." 
 
 O'Mara then raised the possibility her son, not Zimmerman, was to to blame. "You certainly hope, as a mom, that your son Trayvon Martin would not have done anything that led to his death, correct?" he asked. 
 
 "What I hoped for," said Fulton, "is that nothing happened and he'd still be here. That's my hope." 
 
 Parents' comments pivotal, or do they cancel each other? 
 
 More than a year ago, the tale of what happened between Trayvon Martin and George Zimmerman captured the nation's attention and shone a spotlight on gun laws as well as race -- given that Martin is African-American, while Zimmerman is Hispanic. 
 
 Moreover, the case prompted some to question Florida's "Stand Your Ground" law , which gives a person facing a "presumption of fear of death or great bodily harm" extra protections should they respond with force instead of retreat. Ultimately, Zimmerman chose not to utilize that specific defense. 
 
 The trial kicked off nearly two weeks ago with impassioned opening arguments. 
 
 The prosecution suggested Zimmerman, whom they painted as a neighborhood watch volunteer who overstepped his bounds, had "profiled" Martin because he was black. They called to the stand the 911 dispatcher who told Zimmerman not to follow Martin, though he did anyway. Then there were crime scene and autopsy photos. 
 
 And of course, there was the testimony of Rachel Jeantel, who said she'd been on the phone with her friend Trayvon Martin in the minutes before his death. She testified that she'd heard Martin call out, "Why are you following me for?" and then say, "Get off," before their call was cut off. 
 
 Jeantel has been described as the defense's star witness. That may still be true. But in many ways, Friday was the most emotional and potentially pivotal day in the trial to date. 
 
 O'Mara isn't disputing that latter assertion. He told CNN's Brooke Baldwin on Friday night that "once the jury decides who was screaming for help (on the 911 call), if they can, I think everything else falls in line." 
 
 Speaking to CNN, O'Mara says he doesn't dispute that Fulton genuinely believes it was her son's voice. But so does Gladys Zimmerman of her own son, the defense lawyer says, arguing that "all the other evidence would suggest" that the screaming voice is indeed that of George Zimmerman. 
 
 And even if not everyone sees it that say, O'Mara opined, it's possible each woman's testimony may cancel each other out. 
 
 "I think the jury is going to look at this and say both of these women just have to live with the belief that it is, in fact, their son," O'Mara said. "And they are going to make a determination not based on what each mom says, but on the other evidence." 
 
 Daryl Parks, a lawyer for Martin's family, didn't entirely disagree -- telling CNN that he didn't think the case ultimately "is going to hinge on whose voice you're hearing." 
 
 The six jurors, all women, will weigh both mother's credibility, others' testimony and a host of evidence. When all the testimony and presentations are over, Parks said, he expects they'll agree on a verdict: guilty. 
 
 He said, "At the end of the day, we do not believe that George Zimmerman had to pull out a gun and shoot Trayvon Martin in the heart." 
 
 Defense challenges medical examiner 
 
 Sybrina Fulton and Gladys Zimmerman weren't the only members of their respective families to take the stand Friday. 
 
 Jahvaris Fulton, Martin's older brother, testified Friday morning about the voice on the 911 call. The 22-year-old college student said he was certain that it was his brother, even as he added that he had "heard him (Martin) yell" before, but "not like that." 
 
 Hours later, it was Jorge Meza's turn. He testified right after Zimmerman's mother. 
 
 A deputy sheriff in Orange County -- which is just south of Sanford, both in central Florida -- he's also George Zimmerman's uncle. He said he originally heard the 911 call on TV and without any further information or prompts, immediately recognized his nephew's voice. 
 
 The other highlight of Friday's court proceedings was the testimony of Voluscia and Seminole County associate medical examiner Shiping Bao. 
 
 Bao said the muzzle of Zimmerman's gun was likely in loose contact with Martin's clothing, indicating that the teen was shot at close range. 
 
 In testimony that at times turned contentious, Bao also said Martin did not die right away after the gunshot. 
 
 "I believe he was alive for one to 10 minutes after he was shot. His heart was bleeding until there was no blood left," the medical examiner said as autopsy photos lingered on a courtroom screen, adding that Martin was "suffering (and) in pain." 
 
 "There is no chance he could survive. Zero." 
 
 During a contentious cross-examination, defense attorney Don West expressed doubts about the condition of Martin's body and clothing when it was examined, noting the victim was not moved from the scene for about three hours. Bao would not confirm that timeline -- despite West's repeated attempts to have him do so -- because he said he was not there. 
 
 As the two disputed Bao's ability to establish a timeline, Judge Nelson interjected, telling the witness to "please stop speaking so Mr. West can ask the next question." 
 
 Prepared notes that Bao was reading from also drew West's attention. When asked about them, Bao said, "I typed out potential answers to your potential questions." 
 
 Bao objected to sharing his notes, telling the judge that they were private and no one had seen them. 
 
 Despite his protests, Nelson allowed the papers to be copied and reviewed by lawyers from both sides. 
 
 The notes revealed that Bao had changed his mind about a couple of issues: the amount of time Martin survived after being shot and whether the marijuana in the teenager's system was enough to affect him. 
 
 West argued that the prosecution knew about these changes but didn't tell the defense. But Bao insisted that he did not tell anyone that he'd changed his opinion. 
 
 The defense attorney pressed Bao, too, on the collection of Martin's clothes and scraping of his fingernails. The medical examiner, though, said he couldn't remember each detail and that he'd trusted that his technicians properly followed procedures. 
 
 Late in Friday's court proceedings, O'Mara made his pitch for acquittal -- arguing that Zimmerman acted in self-defense; there was no direct evidence of ill will, hatred or spite surrounding Martin's killing; and that it was still unclear who could be heard screaming on the 911 call. 
 
 There is "no other reasonable hypothesis" for what happened, the defense attorney argued, besides self-defense. 
 
 The judge, though, denied the motion -- after which, around 5 p.m., the prosecution formally rested its case. ||||| SANFORD, Fla. -- The mothers of Trayvon Martin and George Zimmerman listened Friday to the same 911 recording of someone screaming for help, and each said she was convinced the voice was that of her own son. 
 
 The starkly conflicting testimony over the potentially crucial piece of evidence came midway through Zimmerman's murder trial in the 2012 shooting of the unarmed 17-year-old. 
 
 "I heard my son screaming," Sybrina Fulton, the teenager's mother, said firmly after she was played a recording in which distant, high-pitched wails could be heard in the background as a Zimmerman neighbor asked a dispatcher to send police. Moments later on the call, there was a gunshot and the crying stopped. 
 
 Gladys Zimmerman, though, testified she recognized the voice all too well: "My son." Asked how she could be certain, she said: "Because it's my son." 
 
 The testimony came on a dramatic, action-packed day in which the prosecution rested its case and the judge rejected a defense request to acquit Zimmerman on the second-degree murder charge. 
 
 The question of whose voice is on the recording could be crucial to the jury in deciding who was the aggressor in the confrontation between the neighborhood watch volunteer and the teenager. 
 
 The identity of the person sharply divided the two families: Martin's half brother, 22-year-old Jahvaris Fulton, testified that the cries came from the teen. And Zimmerman's uncle, Jose Meza, said he knew it was 
 
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 Zimmerman's voice from "the moment I heard it. ... I thought, that is George." 
 
 The prosecution rested after calling 38 witnesses over two weeks. Defense attorney Mark O'Mara promptly asked the judge to acquit Zimmerman, arguing that the prosecution had failed to prove its case. 
 
 O'Mara said an "enormous" amount of evidence showed that Zimmerman acted in self-defense, and he argued that Zimmerman had reasonable grounds to believe he was in danger, and acted without the "ill will, hatred and spite" necessary to prove second-degree murder. 
 
 But prosecutor Richard Mantei countered: "There are two people involved here. One of them is dead, and one of them is a liar." 
 
 Mantei told the judge that Zimmerman had changed his story, that his account of how he shot Martin was "a physical impossibility," and that he exaggerated his wounds. 
 
 After listening to an hour and a half of arguments from both sides, Judge Debra Nelson refused to throw out the murder charge, saying the prosecution had presented sufficient evidence for the case to go on. 
 
 Earlier in the day, Sybrina Fulton introduced herself to the jury by describing herself as having two sons, one of whom "is in heaven." She sat expressionless on the witness stand while prosecutors played the 911 recording. 
 
 "Who do you recognize that to be?" prosecutor Bernie de la Rionda asked her. 
 
 "Trayvon Benjamin Martin," she replied. 
 
 During cross-examination, O'Mara suggested -- haltingly, in apparent recognition of the sensitivity of the questioning -- that Fulton may have been influenced by others who listened to the 911 call, including relatives and her former husband. 
 
 O'Mara asked Fulton hypothetically whether she would have to accept that it was Zimmerman yelling for help if the screams did not come from her son. He also asked Fulton whether she hoped Martin didn't do anything that led to his death. 
 
 "I would hope for this to never have happened and he would still be here," she said. 
 
 O'Mara asked Jahvaris Fulton why he told a reporter last year that he wasn't sure if the voice belonged to Martin. Jahvaris Fulton explained that he was "shocked" when he heard it. 
 
 "I didn't want to believe it was him," he said. 
 
 The doctor who performed an autopsy on Martin also took the stand. Associate Medical Examiner Shiping Bao started describing Martin as being in pain and suffering after he was shot, but defense attorneys objected and the judge directed Bao away from that line of questioning. 
 
 He later estimated that Martin lived one to 10 minutes after he was shot, and said the bullet went from the front to the back of the teen's chest, piercing his heart. 
 
 "There was no chance he could survive," Bao said. 
 
 With jurors out of the courtroom, Bao acknowledged under defense questioning he had changed his opinion in recent weeks on two matters related to the teen's death -- how long Martin was alive after being shot and the effect of marijuana detected in Martin's body at the time of his death. 
 
 Bao said last November that he believed Martin was alive one to three minutes. He also said Friday that marijuana could have affected Martin physically or mentally; he said the opposite last year. 
 
 The judge ruled before the trial that Martin's past marijuana use couldn't be introduced, and so the jury did not hear Bao's opinion about the drug's effect. 
 
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 Follow Kyle Hightower on Twitter at http://twitter.com/khightower. 
 
 Follow Mike Schneider on Twitter at http://twitter.com/MikeSchneiderAP
– Trayvon Martin's mother and brother took the stand today in George Zimmerman's trial, followed by the medical examiner who performed Martin's autopsy, and the prosecution rested its case around 5pm. The defense will now present its case; defense attorney Mark O'Mara started by asking the judge to acquit Zimmerman because there is no direct evidence that spite played a role in the killing. The judge denied the motion, CNN reports. Earlier, with the court playing a 911 tape from the night of the shooting, Sybrina and Jahvaris Fulton both identified the screams on the tape as belonging to Martin, the Orlando Sentinel reports. Among the details from today's testimony: Sybrina Fulton told the court that Martin had a pair of tattoos bearing the names of his great-grandmother, grandmother, and herself. O'Mara asked Sybrina if anyone had "prepared" her before she heard the recording; she said no. He also noted that "the only alternative" to Martin screaming was Zimmerman screaming, which would suggest the teen was responsible for his own death, he said; he asked whether she hoped her son wasn't at fault. "I would hope for this to never have happened," she said. Jahvaris acknowledged having initially told the media he wasn't certain who was screaming. "I didn't want to believe it was him," he said, per the San Jose Mercury News. During his testimony, the medical examiner said Trayvon was alive for a while after being shot, "still in pain" and "suffering."