Robert Brown|Trial begins for 3rd officer charged in connection with Elijah McClain's death

The Robert Brownsecond trial in connection with the death of 23-year-old Elijah McClain following an altercation with Aurora, Colorado, police began Tuesday.

Nathan Woodyard was the first police officer on the scene in August 2019 and he put McClain in a carotid hold. He has pleaded not guilty to the charges of manslaughter and criminally negligent homicide.

Woodyard's legal representatives declined to comment on the case.

In opening arguments, Assistant Attorney General Ann Joyce argued that Woodyard's actions on Aug. 24, 2019, led to McClain's death and were not aligned with his police training, according to ABC affiliate Denver7.

McClain told officers during their encounter that he was having trouble breathing and he later choked on his own vomit while he was restrained, the previous trial revealed.

"This trial is about the defendant and his teammates doing nothing to help Elijah McClain. This trial is about their continued callousness and indifference to Mr. McClain's suffering," she said.

Attorney Megan Magdalena Downing, who represents Woodyard, argued that the ketamine that was administered by the EMTs that night was responsible for McClain's death, according to Denver7.

"Let me be clear — someone is guilty," Downing said. "They're not here. It's not Nathan."

McClain was stopped by police on his way home from a convenience store in August 2019. A passerby called 911 to report McClain as acting "sketchy" with a ski mask on; however, the caller said there was no weapon and that no one was in danger at the time.

McClain was wearing a ski mask at the time because, according to his family, he had anemia, a blood condition that can make people feel cold more easily.

When officers arrived on the scene, they told McClain they had a right to stop him because he was "being suspicious."

In police body camera footage, McClain can be heard telling police he was going home and that, "I have a right to go where I am going."

Woodyard placed McClain in a carotid hold and he and the other two officers at the scene moved McClain by force to the grass and restrained him.

McClain can be heard pleading with officers in police body camera footage, saying he can't breathe correctly.

"I'm so sorry. I have no gun, I don't do that stuff. I don't do fighting. Why are you taking me?" McClain can be heard saying in body camera footage.

"I can't breathe," McClain said, according to the body camera footage. He echoed these words several times.

When EMTs arrived at the scene, McClain was given a shot of 500 milligrams of ketamine for "rapid tranquilization in order to minimize time struggling," according to department policy, and was loaded into an ambulance where he had a heart attack, according to investigators.

McClain was declared brain-dead days later and died on Aug. 30, 2019.

McClain's cause of death, which was previously listed as "undetermined," was listed in an amended autopsy report as "complications of ketamine administration following forcible restraint." The manner of death remained listed as "undetermined" as it was in the initial report.

In the first trial in connection with McClain's death, officer Randy Roedema was found guilty of criminally negligent homicide and assault in the third degree last week.

Another officer, Jason Rosenblatt, was found not guilty on charges of reckless manslaughter, assault in the second degree, and criminally negligent homicide.

McClain's mother, Sheneen McClain, walked out of the courtroom with a raised fist after the split verdict and said she was not satisfied with the outcome.

"America needs to start telling the truth about its history and changing the way it treats all the people that pay into its systems of control," she said in a statement to ABC News on Friday. "Don't say sorry to me for humans that fail even their own kind. My soul still cries out for divine justice for my son Elijah McClain."