And now, to an a b bc news exclusive. For the first time, we are hearing the unmistakable voice of trayvon martin, who was shot to death on the way to see his family. The recording may help answer a... See More
And now, to an a b bc news exclusive. For the first time, we are hearing the unmistakable voice of trayvon martin, who was shot to death on the way to see his family. The recording may help answer a question about what really happened, whose voice is on althou another tape, screaming. Was it martin or george zimmerman, who claimed self-defense? Here's abc's matt gutman. Reporter: His is one of the nation's most recognizable faces, but this may be the first time you'll hear trayvon martin speak. Oh, he coming for that -- Reporter: Abc news exclusively obtained audio from his cellphone. Take a listen as the 17-year-old is heard horsing around with his friends. As he films two homeless men arguing over a bike. We need a behind the scenes. Reporter: That new audio clip could be a pivotal piece of evidence in the trial, when compared with this -- I'm not sure, they are just screaming outside. Reporter: The 911 call the night of the shooting. Do you think they're yelling help? Yes. What is your -- Reporter:14 howls, pleas for help heard in 40 seconds of this 911 call, before the single fatal gunshot that killed martin. We already have a sample of zimmerman's voice, during his reenactment of the shooting for police. He was staring, looking around. Reporter: He claimed it was his voice crying for help. Today in court, both sides argued the tapes should be heard. La . There are standards for voice identification that this case doesn't match. But I can get some results, which indicate that more likely to be zimmerman. Reporter:16 months after his death, martin isn't able to be there in court, but his mother will. How hard is that going to be for you to watch, day after day? I'm sure it will be I'm sure that I'm probably going to see some things I don't want to see and hear some things i don't want to hear. But I'm committed that I have to be there for trayvon. Reporter: It's now up to a judge to decide whether to allow forensic audio experts to testify or whether the jury should bear the burden of becoming the audio experts during this trial.
This transcript has been automatically generated and may not be 100% accurate.