The shooting of Trayvon Martin has ignited passionate responses everywhere, but the only person who knows what really happened the night of the shooting is Martin's killer, George Zimmerman, and he may be lying. However, there's one piece of evidence that could be integral in proving Zimmerman's guilt or innocence: recordings of 911 calls placed by a people living close to where the shooting took place.
You can listen to one of the calls below. While the woman who made the call speaks with the dispatcher, someone can be heard screaming in the background, which abruptly stops after a shot is heard. Martin's family says the screams are Martin pleading for help. Zimmerman says it's him.
Voice-recognition technology could play a key part in finding out whether or not Zimmerman is telling the truth.
"I believe voice identification can be a very beneficial tool that, when used properly, can verify truth behind who said what when," says Ed Primeau, voice-identification expert who has more than 25 years experience with forensic voice analysis.
Primeau isn't involved in the Martin investigation, but he says that, ideally, an ID is made against a recording of someone speaking normally for a few minutes. Analyzing a recording like the 911 call where the voice in question isn't speaking in normal tones, and is in the background is something Primeau describes as "emergency voice identification."
"This case is a little bit different because we've got someone screaming in the background and the phone is picking up what it can," he says. "It's going to be a little more difficult to come up with scientific conclusions, but it's possible. This is an exact science."
If Primeau were to perform the analysis, he says he'd take recordings of Zimmerman's voice speaking in similar tones at various distances 10, 20 and 30 feet and capturing them on a similar device as the caller's phone, essentially trying to recreate the conditions of the original call.
"Let's get a sample of Zimmerman's voice. Let's get him in the backyard yelling with a transcript of what was said. Let's record that and compare it to the 911 call."
Primeau says recordings of Martin's voice would help, too. Even though Martin is no longer alive to provide samples of his voice, Primeau says there are techniques he could apply for example, looking for a person's unique vocal "habits," the way they pronounce certain syllables that might aid in the analysis.
"If there's video of Trayvon, and he's speaking on camera, it would be very helpful. That is definitely the way to go to get a sample of Zimmerman's voice, get some video footage of Trayvon and then this 911 call and come up with a conclusion."
Although a voice analysis of the 911 call would be an extremely helpful tool for investigators, Primeau emphasizes it still needs to be considered in the context of all of the evidence.
"What you do in a criminal matter like this is you take a voice-identification expert's opinion and you add that to the other clues in the case. You don't have the voice-ID guy be the only person who's giving you an opinion of what happened."
How big a role do you think voiceprint analysis will play in solving the Trayvon Martin case? Share your thoughts in the comments.