Trayvon Martin shooting: It's not George Zimmerman crying for help on 911 recording, 2 experts say

As the Trayvon Martin
controversy splinters into a debate about self-defense, a central
question remains: Who was heard crying for help on a 911 call in the
moments before the teen was shot?

A leading expert in the field
of forensic voice identification sought to answer that question by
analyzing the recordings for the Orlando Sentinel.

In the post 9-11 world, Owen says, voice identification is "the main
biometric tool" used to track international criminals, as well as
terrorists.

"These people don't leave fingerprints, but they do still need to talk to one another," he says.

'The home run'

Though the term "biometric analysis" may sound futuristic, it basically
just means using personal characteristics for identification. A
fingerprint scanner is an example of a biometric device.

Much as
the ridges of a human hand produce a fingerprint, each human voice has
unique, distinguishable traits, Owen says. "They're all particular to
the individual."

The technology Owen used to analyze the
Zimmerman tape has a wide range of applications, including national
security and international policing, he said. A recently as January,
Owen used the same technology to identify accused murderer Sheila
Davalloo in a 911 call made almost a decade ago.

Owen testified
that it was Davalloo, accused of stabbing another woman nine times in a
condo in Shippan, Conn., who reported the killing to police from a pay
phone in November 2002.

Davalloo was convicted, according to news reports.

Owen says the audio from Zimmerman's call is much better quality than
the 911 call in the Davalloo case. Voice identification experts judge
the quality based on a signal-to-noise ratio; in other words, comparing
the usable audio in a clip to the environmental noises that make a match
difficult.

And the call on which the screams are heard is better quality than is necessary, Owen says.

"In our world, that's the home run," he says.

Not all experts rely on biometrics. Ed Primeau, a Michigan-based audio
engineer and forensics expert, is not a believer in the technology's use
in courtroom settings.

He relies instead on audio enhancement
and human analysis based on forensic experience. After listening closely
to the 911 tape on which the screams are heard, Primeau also has a
strong opinion.

"I believe that's Trayvon Martin in the
background, without a doubt," Primeau says, stressing that the tone of
the voice is a giveaway. "That's a young man screaming."

Zimmerman's call to authorities minutes before the shooting provides a
good standard for comparison, Primeau says, because it captures his
voice both at rest and in an agitated state.

'CSI' effect

Only one person alive knows
exactly what transpired in the moments immediately before Trayvon was
fatally shot: Zimmerman, who has claimed he fired in self-defense.

Zimmerman told police he was walking back to his SUV after a brief foot pursuit of Martin, and the teen confronted and attacked him, punching him and slamming his head into the pavement.

Arriving police said Zimmerman was bloodied. One officer wrote in a
police report that he overheard Zimmerman telling a paramedic, "I was
yelling for someone to help me, but no one would help me."

Angela
Corey, the special prosecutor assigned to the case, has yet to decide
whether to charge Zimmerman, send the case to a grand jury or decide
against charging.

If Zimmerman's self-defense claim is tested at
trial, legal experts say a forensic identification of the voice in the
911 audio could be key evidence, either in Zimmerman's favor or to his
detriment.

Still, Maine-based audio enhancement expert Arlo West
says that today's juries sometimes seem reluctant to accept evidence
that's any less conclusive than what they're used to seeing on
television.

"I call it the 'CSI' effect," he says, referring to
"CSI: Crime Scene Investigation," the popular — if not always realistic —
forensics-based TV drama. "You get in front of a jury, and they expect a
miracle."