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Zimmerman Trial: Why No 911 Expert Testimony?

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By Brett Snider, Esq. on June 24, 2013 12:58 PM

Expert testimony about cries for help on a 911 call will not be heard at George Zimmerman's murder trial, after the judge ruled Saturday that the testimony was based on unreliable methods.

Although prosecutors and the defense are welcome to have family or other non-expert witnesses testify about the tape, the prosecution won't be allowed to have their forensic voice analysts testify about the identity of the voice heard screaming for help on the tape, reports NBC News.

Opening statements in Zimmerman's trial began Monday. What does the 911 expert testimony ruling mean for the prosecution?

Voice Expert Testimony

Judge Debra Nelson ruled that two audio experts could not be called to testify about the screaming that is heard on the 911 call -- cries for help that may have belonged to Trayvon Martin.

Relatives of both Martin and Zimmerman claim the scream for help is coming from their loved one. Prosecutors had hoped to settle the matter by having forensic voice analysts testify about their "probable findings" that Martin was the one screaming for help, reports Reuters.

This testimony could have gone a long way in disproving Zimmerman's self-defense claim, painting Martin as a scared victim pleading for help and not an attacker.

Reliability of Evidence

Both experts who sought to testify admitted that their findings were tentative. But other experts, including one from the FBI, insisted that their proposed testimony was "not founded in science anywhere," reports The New York Times.

Generally, expert testimony must be considered reliable in order for it to be allowed into evidence. With scientific testimony, there are two major standards accepted by the U.S. Supreme Court: Daubert and Frye.

Florida moved to apply the Daubert test statewide for scientific reliability in April, but not before Judge Nelson applied the Frye standard in the Zimmerman trial.

Frye Standard

The Frye standard or Frye test requires a hearing, outside of the trial, where evidence is presented to support or deny a scientific theory's "general acceptance" in its relevant community.

It is often more difficult for new theories or methods to pass the Frye standard because even if they are scientifically sound, it is quite a different thing to say that they are "generally accepted."

Judge Nelson determined under Frye that the methods used by the prosecution's proposed 911 expert voice witnesses were not generally accepted by the scientific community, so they are not fit to be admitted in Zimmerman's trial.

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