However, Jonathan Good said he did not see anyone's head being slammed into the concrete sidewalk, which Zimmerman has said Martin did to him. Good initially testified that it appeared "there were strikes being thrown, punches being thrown," but during detailed questioning he said he saw only "downward" arm movements being made.
Zimmerman has claimed that he fatally shot 17-year-old Martin last year in self-defense as the Miami-area teen was banging his head into the concrete sidewalk behind the townhomes in a gated community.
But under prosecution questioning, Jonathan Good said he never saw anyone being attacked that way during the fight between Zimmerman and Martin.
"I couldn't see that," Good said moments later while being cross-examined.
Good, the second person to take the witness stand Friday, said he heard a noise behind his townhome in February 2012, and he saw what looked like a tussle when he stepped out onto his patio to see what was happening.
He said he yelled, "What's going on? Stop it."
Good testified he saw a person in black clothing on top of another person with "white or red" clothing. He said he couldn't see faces but it looked like the person on the bottom had lighter skin. Martin was black and was wearing a dark hoodie. Zimmerman identifies as Hispanic and was wearing a red jacket.
"It looked like there were strikes being thrown, punches being thrown," Good said.
Later, under cross-examination, he said that it looked like the person on top was straddling the person on bottom in a mixed-martial arts move known as "ground and pound." When defense attorney Mark O'Mara asked him if the person on top was Martin, Good said, "Correct, that's what it looked like."
Good also said the person on the bottom yelled for help.
During cross-examination, O'Mara got on his knees to recreate the fighting as he asked Good to walk him through it.
Good was in the middle of dialing 911 inside his townhome when he heard a gunshot, he said.
Zimmerman, 29, could get life in prison if convicted of second-degree murder. Zimmerman followed Martin in his truck and called a police dispatch number before he and the teen got into a fight.
Zimmerman has denied the confrontation had anything to do with race, as Martin's family and their supporters have claimed.
A second former neighbor of Zimmerman testified after Good. Jonathan Manalo, whose wife had testified earlier in the week, was the first neighbor to step outside and see what happened with his flashlight after he heard a gunshot. He took cellphone photos of a bloodied Zimmerman and Martin's body, and those photos were shown to jurors on Friday. Manalo also described Martin's hands as being under his body.
Manalo said Zimmerman didn't appear shocked and acted calmly. After police officers arrived and handcuffed Zimmerman, the neighborhood watch volunteer asked Manalo to call his wife and tell her what happened.
Manalo started to tell Zimmerman's wife that her husband had been involved in a shooting and was being questioned by police when "he cut me off and said, 'Just tell her I shot someone,'" Manalo said.
Under cross-examination, Manalo said when he asked Zimmerman what happened, the neighborhood watch volunteer told him, "I was defending myself and I shot him."
"From what you could tell at that moment, that seemed completely true?" asked defense attorney Don West.
"Yes," Manalo said.
The first police officer and the first paramedic to respond to the shooting also testified Friday. Officer Tim Smith testified that when he saw Zimmerman after the shooting, the neighborhood watch volunteer's backside was covered in grass and wetter than his front side, bolstering defense attorneys' contention that Martin was on top of Zimmerman.
Smith said Zimmerman described himself as "lightheaded" during the drive to Sanford Police Station but declined an offer to take him to a hospital.
Paramedic Stacy Livingston said Zimmerman had a swollen, bleeding nose and two cuts on the back of his head an inch long. When O'Mara asked if Zimmerman should have been concerned with his medical well-being because of his injuries, Livingston said, "Possibly."
When photos of Martin's body were shown on a courtroom projector during Livingston's testimony, Martin's mother, Sybrina Fulton, looked away and blinked back tears.