A chief medical examiner from St. Louis flown in as a key expert witness in the administrative trial of a New York City police officer accused of killing Eric Garner several years ago testified Wednesday that a chokehold did not kill Garner, contradicting the ruling of the New York City medical examiner.

Dr. Michael Graham was one of two witnesses that testified before the defense rested its case.

Graham said a chokehold did not kill Garner because he could speak and never lost consciousness.

“It can’t be compression of the neck. He never lost consciousness. He’s talking,” he said.

Graham also testified that he did not think Garner had an asthma attack either. 

“He probably felt that he couldn’t breathe, but he could breathe. Just because he’s complaining of shortness of breath doesn’t mean it’s because of anything happening to his neck,” he said.

Graham said he believes Garner's death was caused by heart problems because "his heart disease was exacerbated by the interaction with law enforcement.”

Graham's testimony contradicts the findings of the city's medical examiner who ruled the chokehold as the cause of death in Garner's passing.

On May 15, describing the chokehold as the first event in a lethal cascade of events, Dr. Floriana Persechino, a medical examiner for New York City, said she found hemorrhages on muscles inside the neck, root of tongue and the back of his neck. She said there was a 2-inch hemorrhage in front of his larynx. The hemorrhages, she said, occurred around the time of Garner's death. She noted that she found no visible injuries under Garner's neck, but said in her medical opinion, the 43-year-old father was put in a chokehold.

Earlier Wednesday, another defense witness -- one who taught officer Daniel Pantaleo at the police academy -- testified the alleged chokehold seen in the famous cell phone video from the 2014 incident was instead a proper procedure called a "seatbelt" maneuver.

"One hand is going over the shoulder," retired NYPD Russell Jung said. "The intent is to get him into a more compliant position for cuffing."

Graham's testimony is the latest development in the administrative trial of  Pantaleo, as was the sight of a federal prosecutor sitting in on the administrative trial Wednesday.

The appearance of Assistant U.S. Attorney Elizabeth Geddes at a proceeding on Wednesday signaled that the Department of Justice still has an interest in how Garner died.

A federal inquiry began after a state grand jury declined to charge Officer Daniel Pantaleo in 2014. Federal authorities are facing a mid-July deadline to decide whether to charge him with civil rights violations.

Pantaleo could be fired if an administrative judge determines he violated NYPD procedures.

Garner's dying words, "I can't breathe," became a slogan for the Black Lives Matter movement.

Outside the trial, shouts of protesters could be heard demanding "Fire Pantaleo!" as the police union president tried to speak over the shouts.

"The manuever that was used was proper and taught in our police academy," PBA president Pat Lynch said.

Garner’s mother, Gwen Carr, was furious that Pantaleo did not testify at this trial. Instead, the judge got a written transcript of his statements to internal affairs.

"Is that fair? Is that justice?" she said.

Wednesday's hearing also brought several city council members and the public advocate to the trial. A case thats ignited racial and political tension.

Prosecutors may call a rebuttal witness Thursday before closing arguments begin. 

The judge has not indicated how long she will take to make a decision.