According to Tracy Martin, the Sanford police recounted this sequence of events: Trayvon Martin walked up to Zimmerman’s vehicle and asked why he was following him. Zimmerman denied following the youth and rolled up the car window. Minutes after Trayvon walked away, Zimmerman got out of his vehicle.
Surely that would be on the 911 tape where Zimmerman says Martin is "checking me out"? But I don't hear it. Why would Zimmerman make that up - he had to know his call was being recorded? Or, why would the cops make that up - to get dad to back down? How's that working?
The Orlando Sentinel contacted the voice identification experts. Both determined it was not George Zimmerman who called for help. Using different methods they took all the screams, put those together, and cut out everything else. You can listen to the extracted screams at the Sentinel’s site.
I didn't find the audio. I found a transcript.
-- Why would Zimmerman make that up --
Why would Tracy Martin make up or misunderstand what he was told by the police? This is not the only incidence of Tracy misunderstanding what the police told him.
-- The Orlando Sentinel contacted the voice identification experts. --
The Orlando Sentinel is invested in preserving its narrative, not in getting to the truth. That said, the experts are running against their own test protocol, which tells them the evidence is insufficient to support a conclusion.