Tracy Martin, the father of the Miami teen who was shot and killed by George Zimmerman in Sanford, was called to testify on Monday.
Trayvon Martin's father was questioned by defense attorney Mark O'Mara about how he said the screaming in the background of a 911 call was not his son.
Tracy Martin said he recalls lead investigator Chris Serino asking him "do you recognize the voice?" Tracy Martin says he answered "I can't tell" and never said "no it wasn't my son's voice."
Tracy Martin denied saying he listened to a "cleaned up" or "enhanced" version of the tape. He also said he never told Martin's mother, Sybrina Fulton, about listening to the tape.
Zimmerman, 29, has pleaded not guilty to second-degree murder for fatally shooting Martin, claiming self-defense.