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Zimmerman trial judge bars expert testimony on 911 call recording

The judge in George Zimmerman's second degree murder trial has decided to bar expert testimony about a 911 call that captured screaming before Trayvon Martin's February 2012 shooting death.

In a written order filed to county court this morning, Judge Debra Nelson called methodologies used by forensic voice analysts seeking to determine who is screaming during the call "not reliable."

However, Nelson said the recording itself can be played at trial -- and left the door open for family and others who knew Zimmerman or Martin to testify about it.

"This order does not prevent the parties from playing the tapes at trial or from calling witnesses familiar with the voice of the Defendant or Martin to testify regarding the identity of the person(s) making the scream," Nelson says.

The decision follows days of testimony from prosecution and defense experts.

Two state experts, forensic voice analysts Tom Owen and Alan Reich, said it was not Zimmerman screaming on the tape.  Reich also said he could discern Martin speaking, claiming he could hear the 17-year-old say "stop" and "I'm begging you" in the moments before he was shot.

But three defense experts testified that the recording was of insufficient length and quality to make a determination, and attacked the research methods used by the state's experts.

In her ruling today, Judge Nelson said there is "no competent evidence that the scientific techniques used by Dr. Owen and Dr. Reich are generally accepted in the scientific field."

That standard -- evidence that the techniques are generally accepted in the field -- was the basis for the so-called Frye Hearing on the science behind voice analysis.

Zimmerman's lawyers had asked for the hearing, seeking to bar Owen and Reich's testimony. 

Reached by phone this morning, George Zimmerman's lead attorney, Mark O'Mara, said he was happy with the decision.

"I thought when I took the case, we'd have the ability to decipher who was who," O'Mara said of the call.  But, he said, he grew to think science couldn't determine the question. 

NBC News reached out to the State Attorney's Office for comment and has not immediately heard back.

Opening statements in Zimmerman's trial begin Monday.

Zimmerman has pleaded not guilty, saying he acted in self defense after Martin attacked him.

Editor’s note: George Zimmerman has sued NBCUniversal for defamation. The company has strongly denied his allegations.