Tracy Martin said he listened to a recording of the call 20 times after his son's death.

"I was listening to my son's last cry for help. I was listening to his life being taken."

But officer Chris Serino said Tracy Martin gave a different answer days after the shooting, when he was asked whether the cries were his son's.

"He looked away, and under his breath, as I interpreted, said no."

Most of the day's testimony centered on the cries.

Former Sanford Police Chief Bill Lee, who was ousted after Martin's shooting, said he would have preferred that family members listened to the tape of the 911 call individually, to prevent group influence.

Instead the Martin family listened together with the mayor, and no law enforcement.

Earlier in the day jurors heard from several of Zimmerman's friends who agreed it was the former Neighborhood Watch volunteer calling for help, not Trayvon Martin.

Sandra Osterman tearfully told defense attorney Mark O'Mara she recognized the voice.

"Yes, definitely it's Georgie," she said.

"And how is it that you know that?"

"I just hear it. I hear him screaming."

The cries for help are at the center of the case. Both the prosecution and defense have used the 911 calls to support their explanation of who the aggressor was in the confrontation between Zimmerman and Trayvon Martin.

Under cross-examination some of the defense witnesses conceded they'd never heard Martin's voice.

Last week Martin's mother Sybrina Fulton testified the voice was her son's.

Prosecutors rested Friday. Zimmerman says he shot and killed Martin in self-defense.