The parents of Trayvon Martin, Tracy Martin, right, and Sybrina Fulton, listen to the testimony of Sanford police officer Chris Serino during the George Zimmerman trial in Seminole Circuit Court, in Sanford, Florida, Monday, July 8, 2013.
Sanford, FL -- Trayvon Martin's dad Tracy took the stand Monday and contradicted the testimony of two Sanford investigators.
Tracy Martin claims he never said the screams heard in the background of a 911 call were not from his son.
"I didn't tell (investigator Chris Serino) 'No, that's not Trayvon,'" Martin said after being called to the stand by the defense.
"I kinda pushed away from the table and shook my head, said 'I can't tell,'" Martin added about what he told Sanford Police two days after the shooting.
Earlier in the day, Serino and Sanford Police Investigator Doris Singleton both testified that Martin told them he did not think it was his son's voice on a 911 call that captured someone screaming out for help, seconds before George Zimmerman fatally shot Trayvon Martin.
While on the stand Monday, Tracy Martin called his son his "best friend," saying his death turned his life upside down.
Monday marked the 10th day of testimony in the Zimmerman trial. If convicted of second degree murder, the neighborhood watch volunteer could be sentenced to life in prison.