Trayvon Martin 911 Call: How Experts ID Voices

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THE GIST

- Biometric voice analysis is the new fingerprinting.

- Software can compare voices to a high degree of scientific certainty.

- With samples of Trayvon Martin's voice, experts may be able to identify screams on 911 tape.

In classic whodunnit mysteries, detectives and FBI agents dust for fingerprints to solve mysteries and collect court-admissible evidence.

In real life, it's more often the voice that offers the tell-tale evidence, since technology to recognize voices in recordings has become so much more sophisticated.

The Feb. 26 recording of a 911 call by a woman who reported someone crying out for help in her gated community in Sanford, Fla., could be a key piece of evidence in the Trayvon Martin murder case, especially since she called early enough so that screams for help and the gunshot were recorded.

George Zimmerman, a Neighborhood Watch volunteer, shot Martin, an unarmed 17-year-old. Why he did so remains a hotly argued topic, with Zimmerman claiming Martin attacked and beat him.

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Tom Owen, a forensic consultant for Owen Forensic Services LLC and chair emeritus for the American Board of Recorded Evidence, recently analyzed the tape. After running the woman's 911 call through a software program called Easy Voice Biometrics and comparing it to another 911 call with Zimmerman's voice, Owen's team concluded that the screams for help were not Zimmerman's.

And, Owen said, if he had samples of Martin's voice, he may be able to definitively identify the screams as his.

"We've talked to the family; the attorney has been notified," he told Discovery News.

How can he be so sure?

Acoustic scientists have been using audio forensics since WWII when, with the aid of the newly invented sound spectrograph, they realized they might be able to identify enemy voices on radio broadcasts. The spectrograph graphed the frequency and amplitude of voice patterns.

The scientists realized the value of that information because, with the possible exception of twins, voiceprints are unique, forensic-audio examiner Stuart Allen told Discovery News.

"Unless you've had surgery, you can't disguise the characteristics of your vocal cords or mouth structure," he said.

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