We turn now to the latest on the case of george zimmerman, the neighborhood watchman accused in the murder of 17-year-old trayvon martin. With jury selection now set to begin monday abc news has... See More
We turn now to the latest on the case of george zimmerman, the neighborhood watchman accused in the murder of 17-year-old trayvon martin. With jury selection now set to begin monday abc news has obtained a potentially significant recording of martin's voice. Abc's matt gutman is in sanford, florida, covering every bit of the case and has the latest. Good morning to you, matt. Reporter: Hey, good morning, josh. One of the biggest mysteries was what was screened on that 911 call heard just moments before trayvon martin was shot. This morning, a judge right behind me will have to rule whether nall cyst of that choppy 911 audio is admissible. This morning, prosecutors and defense lawyers will pick dueling audio experts against each other. I don't follow the difference. It's not unusual for them to have different views. Reporter: Each trying to convince a judge to let jurors hear their analysis of who was screaming on this 911 call made in the moments before trayvon martin was shot. So you think he's yelling help? Yes. What is your -- Reporter: In this reenactment george zimmerman argues the 14 screams were his. Proof he says that he fired that single shot at the 17-year-old in self-defense. But martin's family and prosecutors say the call proves martin was crying for help before he was killed. Oooh, he coming for that -- Reporter: This new audio obtained exclusively by abc news is the first time trayvon martin's voice has been heard publicly. Taken from a video he filmed on his cell phone. We need a behind-the-scenes -- Reporter: Until this recording was uncovered audio experts for the defense had no way to compare martin's voice to the 911 call. A forensic audio expert not affiliated with the trial tells abc news he believes the screams in the 911 call are more likely zimmerman's than martin's. But he says the recording is not clear enough to make a conclusive determination. The 911 recording is probably the best evidence of what happened other than george zimmerman himself and remember, we don't have the testimony from trayvon martin. Reporter: Something his mother, sabrina fulton, is ke keenly aware of. How would you describe the last 15 months? A roller coaster. When I see someone wearing a hoodie, when I see a teenager, everyone reminds me of trayvon. Reporter: Now, that audio we obtained was part of a cache found on trayvon martin's cell phone. Now, the defense has been saying that the prosecution tried to hide that information from them. They'll be back in court this morning.
This transcript has been automatically generated and may not be 100% accurate.