Updated April 14, 2021 at 4:01 PM ET
Former Minneapolis police officer Derek Chauvin's attorney continued to present the defense's case on Wednesday, including calling a medical witness who disputed the conclusions of many experts who testified for the prosecution.
Chauvin is charged with murder and manslaughter in the killing of George Floyd, who died after Chauvin held his knee on Floyd's neck for nine minutes and 29 seconds on Memorial Day last year.
Dr. David Fowler, a retired forensic pathologist who was chief medical examiner for the state of Maryland, testified that in his opinion, the manner of Floyd's death should be classified as "undetermined" rather than "homicide."
The Hennepin County medical examiner, who testified earlier in the trial, had concluded that Floyd's death was a homicide.
Medical experts called by the prosecution have said that low oxygen levels, caused by the restraint, were the cause of Floyd's death. Chauvin's defense has suggested that Floyd's heart condition and drugs in his system were primary factors.
"In my opinion, Mr. Floyd had a sudden cardiac arrhythmia ... due to his atherosclerotic and hypertensive heart disease ... during his restraint and subdual by the police," Fowler said.
In Fowler's determination, "fentanyl and methamphetamine" contributed to Floyd's death. He also said that "there is exposure to vehicle exhaust, so potentially carbon monoxide poisoning or at least an effect from increased carbon monoxide in his bloodstream."
The witness said he did not believe carbon monoxide from the squad car's exhaust caused Floyd's death but said it was potentially a contributing factor.
Questions about Chauvin's restraint
According to testimony, Chauvin's weight was about 140 pounds. Chauvin used a "single-knee technique" in his restraint of Floyd, which Fowler testified would mean that he applied less than 23% of his body weight onto Floyd.
Nelson asked whether Chauvin's knee in any way "impacted the structures of Mr. Floyd's neck."
Fowler replied: "No, it did not. None of the vital structures were in the area where the knee appeared to be from the videos."
Other medical experts in the trial, such as Dr. Jonathan Rich, have said that the restraint and "positional asphyxiation" caused Floyd's oxygen levels to plummet, ultimately resulting in cardiopulmonary arrest.
Fowler said that "all of his injuries were in areas where the knee was not" — the front of the body, his face, places where he was restrained, but not in the back or neck. He said there were not bruises or abrasions on Floyd's neck or back, which he said suggests the amount of force applied to him was less than the amount that causes bruising.
Testimony on cause and manner of death
Fowler concluded that Floyd suffered a sudden cardiac event as a primary cause of death.
He explained the factors that led to his conclusion, including Floyd's enlarged heart, methamphetamine and fentanyl in his system, possible carbon monoxide exposure and narrowed blood vessels.
"There are multiple entities all acting together and adding to each other, and taking away from a different part, of the ability to get oxygen to his heart," Fowler testified. "And so at some point the heart exhausted its reserves of metabolic supply and went into an arrhythmia and then stopped pumping blood effectively."
Fowler contradicted the conclusion made by Dr. Andrew Baker, the Hennepin County medical examiner, that "homicide" was the manner of Floyd's death.
As Baker told the court last week, "In my opinion, the law enforcement subdual, restraint and the neck compression was just more than Mr. Floyd could take, by virtue of those heart conditions." He said he did not believe the drugs in Floyd's system were a direct cause of death.
In Fowler's opinion, the manner of his death should be classified as "undetermined," arguing too many factors were at play to decide which is most accurate.
Prosecution attempts to undermine Fowler's credibility
During his cross examination, prosecuting attorney Jerry Blackwell sought to shake the jury's faith in Fowler's credibility, asking a series of questions to which the pathologist was forced to admit he did not know the answer or had a flawed recollection of the events on May 25, 2020, leading to Floyd's death.
Blackwell first questioned Fowler about the various studies he relied on for his report in determining Floyd's cause of death. The prosecution noted, none of those Fowler referenced involved a victim who had been held in the prone position with the weight of three grown men on top of him for nearly 9 and half minutes.
Fowler agreed they did not.
Blackwell also challenged Fowler's earlier testimony that the absence of bruising on Floyd's neck and back from Chauvin's knees and body weight, as well as that of the other officers, means that they did not cause the 46-year-old's death.
Fowler conceded that in the majority of asphyxia deaths, autopsies often find no physical evidence of bruising or other traumatic injuries.
"In a substantial number of cases" that is true, he said.
The prosecutor then tackled Fowler's theory that carbon monoxide poisoning may have been a contributing factor in Floyd's death.
"You haven't seen any data, or test results, that showed Mr. Floyd had a single injury from carbon monoxide?" he asked.
"Yes, true," Fowler answered, later adding that he did not review any data that Floyd was exposed to carbon monoxide above the levels set by the Environmental Protection Agency.
Blackwell continued to press Fowler, asking if he has ever seen an SUV of the same make and model as squad car 320 in real life.
The pathologist said he had not.
"Did you see any air monitoring data that would give you any information as to what carbon monoxide, if any, would have been in Mr. Floyd's breathing zone?"
He responded: "No because it was not tested."
But one of the most damaging moments for the defense was when Fowler testified that even after Floyd appeared to have lost consciousness after suffering cardiac arrest — about 4 to 5 minutes into the grueling 9 and a half minute restraint — he might been revived had he received immediate medical attention.
"When there is a space between cardiac arrest and between the actual death, are you suggesting that, though Mr. Floyd may have been in cardiac arrest, there was a time when he may have been revived because he wasn't dead yet?," Blackwell asked.
"Immediate medical attention for a person who's gone into cardiac arrest may well reverse that process," Fowler replied.
"Do you feel that Mr. Floyd should have been given immediate emergency attention to try to reverse the cardiac arrest?"
"As a physician, I would agree," he said.
"Are you critical of the fact that he wasn't given immediate emergency care when he went into cardiac arrest?"
"As a physician, I would agree," Fowler repeated.
Fowler faces lawsuit in a Baltimore death-in-custody case
Fowler is one of several parties being sued by the family of Anton Black, a Black 19-year-old who died in police custody in 2018. The Maryland medical examiner's office, which Fowler then led, ruled the death an accident and said there were no signs police did anything wrong, The Baltimore Sun reported.
No officers were charged in Black's death.
"Two years before George Floyd died after being restrained and pinned down by police, 19-year-old Anton Black ... was killed by three white law enforcement officials and a white civilian in a chillingly similar manner on Maryland's Eastern Shore," says the lawsuit filed by Black's family. "This lawsuit arises from the wrongful death of Anton Black at the hands of officers from three different police departments on September 15, 2018, and the ensuing efforts by public officials to protect the officers involved from the consequences of their excessive use of force against a Black teenager."
Chauvin's attorney began laying out the defense's case on Tuesday, including showing police body camera footage of Floyd from a 2019 traffic stop. The jury also heard from witnesses including a woman who was seated in Floyd's car when police approached him last May.
A major component of the prosecution's case has been testimony from other officers and experts who have said that Chauvin's restraint of Floyd was not justified and ran counter to police training.
On Tuesday, the defense attorney called upon Barry Brodd, a former officer and use-of-force expert, who said Chauvin "was justified, was acting with objective reasonableness, following Minneapolis Police Department policy and current standards of law enforcement."
Judge Peter Cahill has said closing arguments in the case will likely begin on Monday.
NPR's Merrit Kennedy contributed to this report.
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