Selene Bahadoor's testimony on Tuesday was the first by someone who saw some of the confrontation that resulted in Martin being fatally shot.
Bahadoor says she heard the sound of running outside the townhome she lived in, and when she looked out a window she saw arms flailing in the dark.
She left to turn off a stove and then heard a gunshot. She says she saw a body on the ground the next time she looked out the window.
Zimmerman is pleading not guilty to second-degree murder, claiming self-defense.
Several times in six months, neighborhood watch captain George Zimmerman called police to report suspicious characters in the gated townhouse community where he lived. Each time, he pointed out that the suspects were black males.
On Tuesday, the judge at Zimmerman's murder trial in the killing of 17-year-old Trayvon Martin listened to the five calls and weighed whether to let the jury hear them, too.
Prosecutors want to use them to bolster their argument that Zimmerman was increasingly frustrated with repeated burglaries and had reached his breaking point the night he shot Martin.
The recordings show Zimmerman's "ill will," prosecutor Richard Mantei told Judge Debra Nelson.
"It shows the context in which the defendant sought out his encounter with Trayvon Martin," Mantei said.
Defense attorney Mark O'Mara argued that the calls were irrelevant and that nothing matters but the seven or eight minutes before Zimmerman fired the deadly shot into Martin's chest.
The prosecution is "going to ask the jury to make a leap from a good, responsible, citizen behavior to seething behavior," O'Mara said.
Prosecutors played the calls with the jurors out of the courtroom at the beginning of a day in which the state presented graphic photos of Martin's body, a police officer described trying to revive Martin as bubbling sounds came from his chest, and a police manager described how she helped Zimmerman set up the neighborhood watch.
In the calls, Zimmerman identifies himself as a neighborhood watch volunteer and recounts that his neighborhood has had a rash of recent break-ins. In one call, he asks that officers respond quickly since the suspects "typically get away quickly."
In another, he describes suspicious black men hanging around a garage and mentions his neighborhood had a recent garage break-in.
Zimmerman, 29, could get life in prison if convicted of second-degree murder for gunning down Martin as the young man walked from a convenience store. Zimmerman followed him in his truck and called a police dispatch number before he and the teen got into a fight.
Zimmerman has claimed self-defense, saying he opened fire after the teenager jumped him and began slamming his head against the concrete sidewalk.
Zimmerman, whose father is white and whose mother is Hispanic, has denied the confrontation with the black teenager had anything to do with race, as Martin's family and its supporters have charged.
On Tuesday, Day 2 of testimony, prosecutors called to the stand a Sanford police sergeant who was the second officer to arrive on the scene. Sgt. Tony Raimondo testified that 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.