The audio conclusions may not be so cut and dry.
"The experts, both of whom said they have testified in cases involving audio analysis, stressed they cannot say who was screaming.
Such analysis could play a role should there be a criminal or civil case over Martin's death. Primeau, who said he uses a combination of critical listening skills and spectrum analysis, called voice identification "an exact science" that can help a legal team in court.
And standards set by the American Board of Recorded Evidence indicate "there must be at least 10 comparable words between two voice samples to reach a minimal decision criteria." While Zimmerman says more than that many words on his 911 call, the only one heard on the second is a cry for "help."
But that board's current chairman Gregg Stutchman -- who described Owens as a friend and well-respected in their field -- said that exact metric doesn't necessarily apply to the software Owens used.
David Faigman, a professor of law at the University of California-Hastings and an expert on the admissibility of scientific evidence, said courts and the overall scientific community have mixed opinions about the reliability of such "voiceprint" analysis.
Because one goal in the Martin case might be ruling out Zimmerman as the source of the screams, rather than precisely identifying who actually was yelling, it could lower the bar for getting such evidence into court, he said."
http://www.cnn.com/2012/04/02/justice/florida-teen-shooting/index.html
I was under the impression, and what I was taught, that an 80% match is necessary for a "positive" identification. CNN is saying 60%. That seems a bit low, to me.
And it looks like my opinion is slightly vindicated:
"Hostin says there are several questions and variables that must be considered, including the fact that the tests did not analyze similar speech. That is, the analysis was based on screams heard from a distance in a 911 call, compared with a direct phone conversation Zimmerman had with a 911 operator.
"Ideally, you want (Zimmerman or Martin's) voice saying the same exact thing, screaming 'help,' in order to analyze it," she said."
http://www.abc2news.com/dpp/news/national/analysts-questions-surround-911-call-analysis-in-trayvon-martin-case