MINNEAPOLIS (NewsNation Now) — A medical expert testifying in defense of former Minneapolis police officer Derek Chauvin told the jury on Wednesday he believed that George Floyd’s death during last May’s arrest was the result of heart disease making his heart beat erratically.

During day 12 of the trial, Chauvin’s attorney Derek Nelson is trying to prove that the 19-year Minneapolis police veteran did what he was trained to do and that Floyd died because of his illegal drug use and underlying health problems.

NewsNation is streaming the trial of Derek Chauvin live on our website.

Chauvin, a 45-year-old white man, is on trial on charges of murder and manslaughter in Floyd’s death after his arrest on suspicion of passing a counterfeit $20 at a neighborhood market. The video of his slow-motion death as he gasped that he couldn’t breathe touched off worldwide protests, violence and a furious examination of racism and policing in the U.S.

Here are the latest updates as court remains in session Wednesday:

DR. DAVID FOWLER, FORENSIC PATHOLOGIST

Dr. David Fowler, a former chief medical examiner for the state of Maryland and now a member of a consulting firm, said the fentanyl and methamphetamine in Floyd’s system were contributing factors, as was Floyd’s heart disease which caused high blood pressure and narrowing of the arteries.

Fowler said the exhaust fumes of the police car against which Chauvin restrained Floyd on the road may also have contributed to Floyd’s death.

“All of those combined to cause Mr. Floyd’s death,” he said on the second day of the defense case.

Fowler appeared to dispute the findings of the Hennepin County medical examiner, who ruled Floyd’s death a homicide caused by police restraining Floyd in a way that starved his body of oxygen.

Prosecutors say Floyd died because Chauvin’s knee was pressed into Floyd’s neck or neck area for 9 1/2 minutes as the 46-year-old Black man lay pinned to the pavement on his stomach last May with his hands cuffed behind his back.

Nelson asked Fowler about Floyd’s narrowed arteries, enlarged heart, use of methamphetamine, the stress of the situation he was in, his high blood pressure and other factors. Fowler said all of them could have caused Floyd’s heart to work harder and led it to suddenly stop.

Previous witnesses have noted that a sudden heart rhythm problem does not necessarily produce visible signs on autopsy but can be inferred from circumstances such as a victim suddenly clutching one’s chest and collapsing.

Several top Minneapolis police officials, including the police chief, have testified that Chauvin used excessive force and violated his training. And a number of medical experts called by prosecutors have said Floyd died from a lack of oxygen because the way he was restrained restricted his breathing.

Fowler said the prone position alone does not affect a person’s ability to breathe — testimony that contradicts other witnesses who said the position Floyd was in, with his hands cuffed behind his back, was inherently dangerous.

He also testified that Chauvin’s knee was not applied with enough pressure to cause any bruises or scrapes on Floyd’s neck or back. He further said that Chauvin’s knee on Floyd was “nowhere close to his airway,” and that Floyd’s speaking and groaning showed that his airway was still open.

And he said Floyd that did not complain of visual changes or other symptoms consistent with hypoxia, or insufficient oxygen to the brain, and that he was coherent until shortly before he suddenly stopped moving.

“The bottom line is, moving air in and out, and speaking and making noise is very good evidence that the airway was not closed,” Fowler said.

Fowler handled a case similar to Floyd’s in Maryland in 2018, when a 19-year-old Black man, Anton Black, died after three officers and a civilian pinned him for more than five minutes as they handcuffed him and shackled his legs.

The family brought a federal lawsuit that included Fowler, whose autopsy found that the stress of the struggle probably contributed to Black’s death but found no evidence that restraint directly caused it. It also found no evidence of asphyxia.

JUDGE REJECTS REQUEST FOR AQUITTAL

Earlier Wednesday, Judge Peter Cahill turned down a defense request to acquit Chauvin, rejecting claims that prosecutors failed to prove Chauvin’s actions killed the Black man.

Cahill pressed on with the case after Chauvin attorney Eric Nelson said the prosecution’s expert witnesses gave conflicting opinions about what caused Floyd’s death after the 46-year-old was pinned under the white officer’s knee for what authorities say was 9 1/2 minutes last May.

Nelson also argued that the state failed to establish whether there was a use of force and whether it was reasonable.

Prosecutor Steve Schleicher countered by saying the state has proved that Chauvin used unreasonable force, and he said it has also introduced evidence that “clearly established that the defendant’s conduct was a causal factor in bringing about Mr. Floyd’s death.”

Requests for an acquittal are routinely made midway through a trial and are usually denied.

DEFENSE CONTINUES FOR SECOND DAY

The trial is currently on Day Two of the defense presenting its case. The prosecution rested its own case on Tuesday after 11 days of testimony and a profusion of video evidence.

The defense hasn’t said whether Chauvin will take the stand.

Testifying could open him up to devastating cross-examination, with prosecutors replaying the video of Floyd’s arrest and forcing Chauvin, one freeze-frame moment at a time, to explain why he kept pressing down on Floyd.

But taking the stand could also give the jury the opportunity to see any remorse or sympathy Chauvin might feel. It would give jurors a good look at his face; he has had to wear a COVID-19 mask while seated at the defense table.

Nelson began his case on Tuesday by challenging the heart of the case against Chauvin, calling a use-of-force expert who testified that Chauvin was justified in pinning Floyd and keeping him down and that it might have gone easier if only Floyd had stopped struggling and began “resting comfortably” on the pavement.

Several top Minneapolis police officials, including the police chief, have testified that Chauvin used excessive force and violated his training. And a number of medical experts called by prosecutors have said that Floyd died from a lack of oxygen because of the way he was restrained.

However, the chief county medical examiner who ruled Floyd’s death a homicide, Dr. Andrew Baker, did not identify lack of oxygen, or asphyxia, as the cause of death. When he took the stand for the prosecution, he testified that Floyd had severe underlying heart disease and an enlarged heart, and that the way he was held down was more than Floyd’s heart could take.

The question of what is reasonable is important: Police officers are allowed certain latitude to use deadly force when someone puts the officer or other people in danger. Legal experts say a key issue for the jury will be whether Chauvin’s actions were reasonable in those specific circumstances.