Voice forensics experts cast doubt on Orlando Sentinel analysis of Trayvon Martin 911 tape

‘Naïve’ voice recognition

The Sentinel also contracted with Ed Primeau, a trained audio engineer and registered investigator whose expert testimony has been used in dozens of criminal court proceedings. Primeau used a more intuitive approach to determine that Zimmerman was not the person heard screaming on the 911 call.

“That’s a young man screaming,” Primeau told the Sentinel.

Comparing the human voice to a symphony full of varying timbres, Primeau wrote on his blog that the “male voice yelling for help … cracks like teen male’s does when going through puberty.”

Dr. Philip Rose of the Australian National University told TheDC that scientific experts refer to Primeau’s method as “naïve voice recognition.” His influential 2002 book Forensic Speaker Identification draws a major distinction between naïve and “technical forensics” voice recognition.

“Naïve voice recognition is so prone to error that it is acknowledged that it is worthless as evidence,” Rose said via email.

A forensic expert’s job, he said, is to assess the strength of evidence, not to estimate the probability of a hypothesis. And “the value of the evidence depends … on the similarity of the samples.”

In a properly conducted analysis, he told TheDC, “you would still have to do the comparison using screamed and phone samples, with many speakers.”

One voice authentication expert whose work is commercial in nature told TheDC that screaming, stress, and a recording’s audio quality can “wreak havoc” on voice biometric software and its ability to interpret data.

And speaking of Owen’s findings, another industry insider said that “a legitimate biometrics expert would likely refute the contentions” and suggests that these were “incendiary publicity plays.”

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