Zimmerman, who told police he shot 17-year-old Martin in self-defense, told a paramedic who arrived on the scene: "I was yelling for someone to help me, but no one would help me." The police report says Zimmerman, 28, was bloodied when police arrived, after Martin allegedly attacked him, punching him and slamming his head into the pavement.
When a neighbor called 911 to report a disturbance, cries for help are clearly heard in the background of the call, followed by gunshots. Experts in biometric audio analysis such as Tom Owen, forensic consultant for Owen Forensic Services LLC and court-qualified expert witness, have analyzed the recording of the call using sophisticated software.
"I took all of the screams and put those together, and cut out everything else," Owen told the Orlando Sentinel. He then compared the screams to recordings of Zimmerman's voice from his own 911 call moments later. The software found there to be a 48 percent match between them. "As a result of that, you can say with reasonable scientific certainty that it's not Zimmerman."
Because no recordings of Martin's voice exist for use in comparison, it cannot be said with certainty whether or not those were his screams heard in the background. However, Ed Primeau, audio engineer and forensics expert, says the tone of the voice is that of a young man.
"I believe that's Trayvon Martin in the background, without a doubt," he said. "That's a young man screaming."
The case is still under investigation, and prosecutor Angela Corey has yet to decide whether to charge Zimmerman. Because the usefulness of audio evidence in the courtroom is disputed, it remains to be seen how useful Primeau and Owen's findings will be in the event Zimmerman goes to trial.
Notable deaths of 2014 [PHOTOS]