SANFORD, Fla. - We're learning more about one of the biggest and most controversial pieces of evidence in the Trayvon Martin case. In 911 calls from a witness, you can hear someone screaming in the background, along with a gunshot.
There's been a lot of speculation about who is screaming in the background of that call - Martin or George Zimmerman? At this point, police in Sanford aren't sure.
Both the Orlando Sentinel and CNN brought in audio experts to enhance the call and compare it to Zimmerman's voice, which was heard on a separate 911 call.
A computer program found that there's a 48 percent chance that Zimmerman is screaming in the background.
The expert from CNN says that this shows we're most likely hearing Martin crying for help.
"There's a huge chance that this is not Zimmerman's voice," says Edward John Primeau, an audio engineer.
"As a matter of fact, after 28 years of doing this I would put my reputation on the line and say this is not George Zimmerman screaming," Primeau says.
But he adds that it's hard to confirm if the screaming came from Martin, because there are no voice samples from the teen to compare the screaming to.
A lot of people involved in the case have their own opinions about who is screaming on that call.
Martin's parents think it's definitely their son. But his brother told Local 6 that he isn't so sure.
Meanwhile, Zimmerman's father and brother both say that Zimmerman is the one shouting in the background.
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