Trayvon Martin case audio: Screams were not George Zimmerman's, 2 experts say The family of a black teenager killed by a neighborhood watch captain say the 911 tapes of the incident, released on Friday, prove George Zimmerman did not act in self-defense... By msnbc.com staff The voice heard crying for help on a 911 call just before Trayvon Martin was shot to death was not that of George Zimmerman, according to two forensic voice identification experts, the Orlando Sentinel reported Saturday. Tom Owen, forensic consultant for Owen Forensic Services LLC and chair emeritus for the American Board of Recorded Evidence, told the Sentinel that he used voice identification software to rule out Zimmerman. Zimmerman told police that he screamed for help during his confrontation with Martin, 17. He claims the shooting was self-defense. The 911 call came on the night of Feb. 26 from a woman who reported someone crying out for help in a gated community in Sanford, Fla. In the recording of her phone call, panicked cries and a gunshot are heard. The Sentinel said it contacted Owen, who it described as a court-qualified expert witness and former chief engineer for the New York Public Library's Rodgers and Hammerstein Archives of Recorded Sound. He told the newspaper he used software called Easy Voice Biometrics to compare Zimmerman's voice to the 911 call screams. Owen told the newspaper that the software compared the screams to Zimmerman's voice and returned a 48 percent match. He said he would expect a match of higher than 90 percent, considering the quality of the audio. "As a result of that, you can say with reasonable scientific certainty that it's not Zimmerman," Owen told the Sentinel. But he also said he could not confirm the voice as Trayvon's, because he didn't have a sample of the teen's voice. The Sentinel said that Ed Primeau, a Michigan-based audio engineer and forensics expert, used audio enhancement and human analysis and came to the same conclusion. Thousands of Trayvon supporters march to police station "I believe that's Trayvon Martin in the background, without a doubt," Primeau told the newspaper. That's a young man screaming. On Feb. 26, Zimmerman, a white Hispanic, had called 911 to report a "suspicious" person and followed Martin against the dispatcher's advice. Martin and Zimmerman grappled, and Martin was shot in the chest. Zimmerman told police that he was walking back to his vehicle when Martin attacked him and slammed his head against the ground and that he shot in self defense. Police declined to arrest Zimmerman citing Florida's "Stand Your Ground" law, which gives wide latitude to use deadly force when a threat is perceived. The lack of an arrest in the case has brought protests across the country. In Sanford on Saturday, thousands of protesters marched to the police station.