"When you're on top you have gravity working for you," Pollock said, adding that punches from above carry more force.

Pollock waved to Zimmerman, who joined the gym in 2010 wanting to lose weight and get in shape. Zimmerman wanted to learn boxing but did grappling, Pollock said. Pollock described Zimmerman as "physically not an accomplished individual." He was a 0.5 on a scale of 1 to 10, Pollock said and after working for many months, Zimmerman rose to a 1.5 out of 10 but was "physically soft."

Zimmerman tried boxing as well but wasn't skilled enough to be in the ring, Pollock said. After the shooting, Pollock described Zimmerman as being "a human being who had been through an extremely traumatizing experience."

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Sondra Osterman was the first defense witness called to the stand on Monday. Her husband, Mark, an air marshal testified earlier in the trial. Osterman said she has known Zimmerman since 2006.

Osterman listened to the screams on the background of the 911 calls, which captured the confrontation between Zimmerman and 17-year-old Martin shortly before Zimmerman fatally shot Martin.

Defense attorney Mark O'Mara asked if her friendship with Zimmerman would affect her opinion.

"I wouldn't lie for him or anybody," Osterman said. O'Mara asked if she knew whose screams they were.

"That's definitely Georgie,"  Osterman said.

Prosector Bernie de la Rionda asked Osterman about the book she co-wrote with her husband, in which proceeds will be donated to Zimmerman after the trial. Osterman said she doesn't know how many books have sold and the money is being put in their savings account for Zimmerman after the trial.

De la Rionda then played the non-emergency 911 call where Zimmerman says "these a******* always get away" and "f****** punks." Osterman identified the voice as Zimmerman.

During redirect, O'Mara asked if Osterman had heard Zimmerman scream like that before, to which she said she hasn't. He also asked if there was anything in the call that was said with spite, hatred anger or ill will, to which she said no.

"Aren't you just speculating about Zimmerman's state of mind the night of the shooting?" de la Rionda asked during redirect.

"We both are," Osterman replied.

The defense then called Mark Osterman to testify. Mark Osterman, who says he's Zimmerman's best friend, testified for the state last week and said he advised Zimmerman on the type of gun to buy if he were going to get a concealed weapons permit.

The 911 call was played again in court and Mark Osterman said the voice is Zimmerman, based on the tone.

During cross-examination, de la Rionda questioned Mark Osterman on the book and how many copies were sold. Osterman said he wasn't sure.

De la Rionda also asked Mark Osterman on what he taught Zimmerman about guns.

"You made him a better shooter?" de la Rionda asked.

"I hope so," Mark Osterman replied.

The defense's third witness of the day on Monday was Geri Russo, who works at Digital Risk--Zimmerman's employer at the time of the shooting.

Russo testified the screams in the background of the 911 call was Zimmerman. The defense hopes their five testimonies of Zimmerman scream identifications outweigh the state's two witnesses for the jury.

During cross-examination, prosecutor John Guy mentioned testing between Russo and Zimmerman.

"My immediate reaction was that's George's voice," Russo said.

The fourth witness of Monday and the sixth overall was Leeanne Benjamin, a realtor who referred clients to Zimmerman when he was into insurance in 2003. She encouraged Zimmerman to go to college and said she was proud of Zimmerman for tutoring young children.

Benjamin said her friendship with Zimmerman wouldn't change her testimony before the state had Benjamin listen to the 911 calls with the screaming in the background. She said the screaming was Zimmerman and that she's heard Zimmerman's voice in a "very similar" manner.