On Tuesday, Day 2 of testimony, prosecutors called to the stand a former Zimmerman neighbor, Selene Bahadoor, the first witness to say she saw part of the struggle.
She described the sound of movement from left to right outside her townhouse and said she heard what sounded like someone saying, "No" or "Uh."
She said that when she looked out a window she saw arms flailing in the dark. She said she left to turn off a stove and then heard a gunshot. The next time she looked out, she saw a body on the ground, she testified.
In cross-examining her, O'Mara accused Bahadoor of never mentioning the left-to-right movement in previous interviews.
Zimmerman contends he lost track of Martin and was returning to his car when he was attacked. But Bahadoor's testimony appeared to suggest Zimmerman was moving away from his vehicle.
O'Mara later confronted her with a post she made on Facebook in which she "liked" a petition that championed the arrest of Zimmerman following the shooting.
A Sanford police sergeant who was the second officer to arrive on the scene also testified. Sgt. Tony Raimondo said he tried to seal a bullet wound in Martin's chest with a plastic bag and attempted mouth-to-mouth resuscitation.
Bubbling sounds indicated air was escaping the teen's chest, Raimondo said. Martin was pronounced dead a short time later.
During Raimondo's testimony, prosecutors showed jurors a photo of a dead Martin face-down in the grass, another of Martin's body face up with his eyes slightly open, and a third of the bullet wound. Martin's father, Tracy Martin, walked out of the courtroom during the testimony.
Wendy Dorival, former coordinator of the Sanford Police Department's neighborhood watch program, testified how she had worked with Zimmerman to set up a watch in his neighborhood.
When asked by prosecutor John Guy if neighborhood watch participants should follow or engage with suspicious people, she said no.
"They are the eyes and ears of law enforcement," Dorival said. "They're not supposed to take matters into their own hands."
Similarly, Donald O'Brien, president of Zimmerman's homeowners association, said it was his understanding that neighborhood watch members are supposed to "stay at a safe distance" and "let the police handle it."
But Dorival said she was impressed with Zimmerman's professionalism and dedication to his community.
"He seemed like he really wanted to make changes in his community, to make it better," she said.