"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 your 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.