- 07.09.13 07:10 AM EDT
George Zimmerman's defense called Trayvon Martin's father, Tracy, to the stand to testify on Monday. Zimmerman, 29, is on trial for killing 17-year-old Trayvon last year, in what Zimmerman claims is self-defense.
In a new turn in the trial, Tracy Martin contradicted earlier testimony from police. Martin said that initially when he heard a recording of the 911 call at the center of the case, he did not know if the voice on it belonged to his son, Trayvon -- and described how upset he was at the time, listening to the shot that had ended Trayvon's life.
This went against earlier testimony, when the lead detective in the case testified that Trayvon's father said that it was not his son's voice on the much-disputed 911 call. Before the trial began, a judge ruled that the jury would be allowed to hear audio from a 911 call recorded on the night of Trayvon's death, but not to hear expert testimony on whether the screams belong to Martin or Zimmerman -- since there was no clear scientific consensus.
On the stand, the defense also grilled Martin about his response on the night of the killing, how he felt when we found out his son has died and why he'd listened to the tape over and over again.
The highly publicized Zimmerman trial in his its third week.