Video via The Orlando SentinelVideo via The Orlando SentinelListening to the the screams in the background of a 911 call placed during the fight that ended in Trayvon Martin's death, I find it hard to believe that anyone can be sure who was the source of those muffled and barely decipherable sounds: Martin or George Zimmerman, the man who shot and killed him. But based purely on the testimony presented during Zimmerman's murder trial, the evidence favors his claim that he was the one crying for help immediately before the gunshot. On Friday two witnesses—Zimmerman's mother and uncle—said they recognized the defendant's voice in the recording of the call, and today four more witnesses—all friends of Zimmerman—said the same thing. None expressed any doubt under cross-examination.

By comparison, while Martin's mother expressed equal certainty during her testimony on Friday that the voice was her son's, two other prosecution witnesses seemed less sure. Martin's older brother claimed on the stand last week that he recognized Martin's voice, but he initially told a reporter he did not know who was screaming. When she took the stand the week before last, Rachel Jeantel, the friend who was talking to Martin on the phone when the fight started, likewise confidently identified him as the person screaming during the 911 call.  But she was much less certain about that in a pre-trial deposition, saying the voice "could be Trayvon," adding, "Like I said, I don't know. But it could be. The dude sound kinda like Trayvon." Today the defense presented testimony from Martin's father, who told police the voice on the recording was not his son's.  On the stand, Tracy Martin said that when police played the recording for him, "[I] just kind of shook my head and said, 'I can't tell.' I never said, 'No, that's not my son's voice.'" But two Sanford police officers testified that was the gist of what he said. Weeks later, after listening to the recording over and over again, "I knew that it was Trayvon’s voice," Tracy Martin testified.

All these witnesses, of course, have strong incentives to hear (or claim to hear) whatever favors the side of the case they favor, and it may be that the ones who have expressed doubts are simply more honest (or less self-deluded) than the rest. A voice analysis expert who has testified for both the defense (during a pre-trial hearing) and the prosecution (during the trial) said the recording was too short and indistinct for any conclusions to be drawn about who was screaming. But if the jury gives any weight at all to the dueling claims of friends and relatives, the testimony helps the defense more than the prosecution. Even a draw on this issue would be a win for Zimmerman, since all he needs to do is create reasonable doubt about the state's narrative, according to which Martin was calling for help and/or begging for his life before he was shot.