The ruling is a victory for George Zimmerman, the Neighborhood Watch volunteer charged with second-degree murder, the Orlando (Fla.) Sentinel reported. Lawyers are scheduled to give opening arguments Monday in his trial in Sanford, Fla.
Prosecutors say Zimmerman trailed Martin, 17, through a gated community in Sanford and then shot and killed him. Martin was walking from a convenience store to a relative's house Feb. 26, 2012, while talking to a girlfriend on his cellphone and was unarmed.
Defense lawyers say Martin attacked Zimmerman, forcing him to fire in self-defense.
Audio expert Alan Reich testified in a preliminary hearing he had determined it was Martin calling "I'm begging you" and "stop" on the 911 tape. Prosecution expert, Tom Owen, said the voice was definitely not Zimmerman.
Judge Debra Nelson said Saturday prosecutors did not show the techniques Reich and Owen used are widely accepted in their field. She said none of the five other experts backed Reich's findings and most said the tape is too poor in quality to do proper voice-recognition analysis, CNN reported.
"There is no competent evidence that the scientific techniques used by Mr. Owen and Dr. Reich are generally accepted in the scientific field," Nelson said. "There is no evidence to establish that their scientific techniques have been tested and found reliable."