(CNN) -- A prosecution witness testified in the George Zimmerman trial Friday that he saw the former neighborhood watch captain on the bottom of a mixed martial arts-style fight with 17-year-old Trayvon Martin the night Martin was fatally shot.
Jonathan Good said he heard a faint noise coming from the back of his home in the Retreat at Twin Lakes on Feb. 26, 2012. When he heard a louder noise, he went outside to investigate. He said he saw two men engaged in a "tussle" on the ground.
Good was the 17th witness to take the stand in the trial of Zimmerman, who is charged with second-degree murder in the shooting of Martin in Sanford, Florida. Zimmerman told police he followed the teenager because there had been some recent break-ins in the area. He says he was forced to shoot Martin during their confrontation in self-defense.
On the trial's fifth day, Good recounted being 15 to 20 feet away from the fight between Zimmerman and Martin. Although he couldn't make out the faces of the people on the ground, Good said he could make out the color of their clothes.
In crucial testimony that appears to buttress the defense's argument, Good said the person on top during the fight was wearing a black top like the black hoodie sweatshirt Martin had on that night, and the person on the bottom was wearing red. Zimmerman was wearing a similar color that night.
Good said it seemed like the person on the bottom was yelling for help. Good said he saw the person on top "straddling" the person on the bottom and the person on top was moving their hands in a downward striking motion that looked like what he called a "ground and pound," a term associated with MMA or mixed martial arts fighting.
"It looked like that position was a ground-and-pound-type position, but I couldn't tell 100% that there were actually fists hitting faces," Good said.
Defense attorney Mark O'Mara asked Good to define the term "ground and pound."
"It's usually when someone is on top in a mounted position, I believe, in the dominant position, but like I said the person on the bottom is able to throw punches back, but I did not see any of that," said Good.
Good said he went outside and called out to Zimmerman and Martin to "cut it out," but after getting no response he went back inside and called 911 -- that's when he heard a gunshot.
"I just heard a shot right behind my house," Good said on the 911 call, which was played in the courtroom. "They are wrestling right in the back of my porch."
Timothy Smith, the first police officer to arrive at the scene, also testified on Friday, making some observations about Zimmerman's clothing that seemed to support Good's version of events.
In regard to Zimmerman's jacket, Smith said, "The back of it was wetter than the front of it. It was also covered in grass." He also described the back of Zimmerman's jeans as "wetter than the front" and agreed that this was consistent with someone lying on his back in the wet grass.
Smith said that when he asked Zimmerman if he saw who shot the person on the ground, Zimmerman told him he was responsible and that he was still armed. Smith said he proceeded to remove his own weapon and point it at Zimmerman. He then handcuffed Zimmerman and eventually took his weapon away.
On their way to the patrol car, Smith said Zimmerman volunteered some information about the scuffle.
"He stated to me that he was yelling for 'help' and that nobody would come help him," said Smith.
Zimmerman repeated the statement once they got to the car, according to Smith.
"It was almost confusion. Sort of a confused look on his face," Smith said.
Defense attorney O'Mara asked Smith if Zimmerman seemed angry, frustrated, spiteful, cavalier or if he appeared to have any ill will or hatred that night. Smith said no to each individual description and called Zimmerman compliant throughout the entire ordeal.
Another neighbor named Jonathan Manalo, who was the first to approach Zimmerman after the shooting, was also asked to describe Zimmerman's behavior that night.
"He wasn't acting like anything different. He was coherent, he was responding to my questions just like any other person," Manalo said.
Defense attorney Don West asked Manalo if Zimmerman told him, "This guy was beating me up and I shot him."
"I was defending myself and I shot him," said Manalo in response.
An EMT who treated Zimmerman at the scene described his injuries to jurors.
"He had a very swollen, bleeding nose. He had lacerations to the back of his head," said Stacey Livingston. "We just tried to clean up his injuries so we could see them better."
The physician assistant who treated Zimmerman the day after the shooting, Lindzee Folgate, said he came in wanting a note to go back to work. He was also complaining of nose pain and told her he was involved in an altercation and was pushed to the ground.
"His head was hit into the pavement multiple times," Folgate said.
She measured two lacerations that she observed on the back of Zimmerman's head, which were 2 cm and 0.5 cm in length. She said she didn't feel sutures were necessary.
She also examined Zimmerman's nose, finding swelling and bruising. Based on her observations, she believed it was broken but couldn't say for sure without an x-ray. She said she encouraged Zimmerman to see a specialist.
Prosecutor Bernie de la Rionda had Folgate review medical records from her past visits with Zimmerman, the first of which was dated Aug. 19, 2011. Zimmerman told her he was having trouble sleeping and had "started to exercise intensely with MMA but this has not helped."
In another visit dated Sept. 23, 2011, Zimmermann told Folgate he was "involved in mixed martial arts three days per week."
Folgate didn't note any swelling on Zimmerman's head the day after he shot Martin, but she did review police photos from that night with defense attorney O'Mara.
She agreed that what appeared to be bumps, swelling and abrasions could be consistent with a head being hit against concrete. But she also said some bumps just occur naturally on the head, depending on the shape.
In his final questions for Folgate, O'Mara asked her whether Zimmerman's life may have been in danger.
"Medically speaking, would you agree that whatever he did to stop the attack allowed him to survive it?" asked O'Mara.
"It could have, potentially, yeah. It depends on the amount of trauma he was sustaining at the time," said Folgate.
"So, stopping the attack is what allowed him to survive it, would you agree?" asked O'Mara.
"It could have, yes," said Folgate.
Prosecutor de la Rionda followed up by asking Folgate if she was speculating. She admitted that she wasn't there that night.
Testimony in the trial is set to resume on Monday at 9 a.m. ET.