How Experts Decided Tape Not Zimmerman

Since news broke over the weekend that two audio experts say the screams for help recorded on a 911 call were not George Zimmerman's voice, I've been wondering how they did their tests. It turns out they used two totally different techniques.

After the Sentinel contacted Owen, he used software called Easy Voice Biometrics to compare Zimmerman's voice to the 911 call screams. "I took all of the screams and put those together, and cut out everything else," Owen says.

Owen, a court-qualified expert witness and former chief engineer for the New York Public Library's Rodgers and Hammerstein Archives of Recorded Sound, is an authority on biometric voice analysis — a computerized process comparing attributes of voices to determine whether they match.

While the story in the Orlando Sentinel, which engaged the experts, goes into great detail on the work that Owen did, it leaves unclear whether the second expert, Ed Primeau, even did any tests on the tape.

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."