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Apr. 8 highlights for the murder trial of Derek Chauvin Day 9

Highlights from Day 9 of the trial of Derek Chauvin. A pulmonologist and forensic toxicologist took the stand in the trial for the death of George Floyd.
Image: The trial of former police officer Derek Chauvin
Activist Stephen Parlato stands outside the Hennepin County Government Center during the trial of former police officer Derek Chauvin, in Minneapolis, Minn., on April 7, 2021.Nicholas Pfosi / Reuters

Live coverage on this blog has ended, please click here for the latest in Derek Chauvin's trial.

Two medical doctors and a forensic toxicologist testified on Thursday in Derek Chauvin's murder trial in the death of George Floyd. Both doctors testified that Floyd died of a lack of oxygen after he was pinned to the ground with his hands cuffed behind him and Chauvin's knee on his neck. The forensic toxicologist said that the fentanyl found in Floyd’s system was lower than levels found in 94% of DUI cases.

Hennepin County Medical Examiner, Dr. Andrew Baker, is expected to testify on Friday. The medical examiner said an autopsy listed Floyd's cause of death as a "cardiopulmonary arrest complicating law enforcement subdual, restraint, and neck compression."

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Dr. Martin Tobin, expert on breathing, testifies half of Derek Chauvin's body weight was on George Floyd's neck

Dr. Martin Tobin, a world-renowned expert on breathing, testified as jurors were shown a photo in which Derek Chauvin's toe is lifted slightly off the pavement as he kneels on George Floyd's neck.

Tobin says that by his calculation, at one point, 91.5 pounds — half of Chauvin's body weight and half the weight of his gear — was on Floyd's neck.

"This means that all of his body weight is being directed down at Mr. Floyd's neck," Tobin said.

Pulmonary expert says knee on Floyd's neck 'extremely important' when considering lack of oxygen

A pulmonary expert testified Thursday morning about why the knee on George Floyd’s neck and back was “extremely important” when considering what caused the lack of breathing that led to his death.

Dr. Martin Tobin loosened his tie, unbuttoned the top button on his shirt and instructed the jurors to feel their necks as he testified about why a knee on the neck was so important.

He said that a knee on Floyd’s neck was “extremely important because it's going to occlude the air getting in through the passageway.”

He walked the jurors through a demonstration of their own neck anatomy, pointing them to the  hypopharynx, which he called “vulnerable.”

“The hypopharynx is very important for understanding this case for a number of reasons. Because it's so vulnerable, because it has no cartilage around it, it's going to be an area that is compressed,” he said. “It's extremely small to breathe through and it becomes very important for being able to continue to breathe through."

Tobin added that Chauvin's knee was on that area of Floyd's neck at points, with enough pressure to cut off his breathing.

Pulmonologist: Derek Chauvin's knee among four forces that caused shallow breathing that led to George Floyd's death

Dr. Martin Tobin, a pulmonologist, testified Thursday that he believes there were four forces that caused George Floyd's shallow breathing and led to his death. 

"The main forces that are going to lead to the shallow breath are going to be that he's turned prone on the street, that he has the handcuffs in place combined with the street and then that he has a knee on his neck and then that he has a knee on his back and on his side," Hines said. "All of these four forces are ultimately going to result in the low tidal volume, which gives you the shallow breaths that we saw here." 

The prosecution has argued that George Floyd died from Derek Chauvin kneeling on his neck for more than 9 minutes.

Pulmonary doctor testifies George Floyd died of 'low level of oxygen'

The first witness called Thursday in the murder trial of Derek Chauvin was a physician in pulmonary and critical care medicine who said George Floyd died from a "low level of oxygen."

Dr. Martin Tobin is a physician with the Edward Hines Jr. VA Hospital and Loyola University Medical School in Chicago. He has been working in respiratory physiology for about 46 years and has served as an expert witness in court before.

Tobin said he was asked to review medical records and watch videos related to the case. He said he believed Floyd died of a "low level of oxygen" that caused damage to his brain and also led his heart to stop beating.

The state is expected to call multiple medical experts over the next two days.

Expert: Chauvin never took knee off Floyd's neck area

MINNEAPOLIS — Officer Derek Chauvin had his knee on George Floyd’s neck — and was bearing down with most of his weight — the entire 9 1/2 minutes the Black man lay facedown with his hands cuffed behind his back, a use-of-force expert testified Wednesday at Chauvin’s murder trial.

Jody Stiger, a Los Angeles Police Department sergeant serving as a prosecution witness, said that based on his review of video evidence, Chauvin knelt on Floyd's neck or neck area from the time officers put Floyd on the ground until paramedics arrived.

“That particular force did not change during the entire restraint period?” prosecutor Steve Schleicher asked as he showed the jury a composite image of five photos taken from the various videos of the arrest.

“Correct,” Stiger replied.

How Derek Chauvin's trial is bringing down the blue wall

During his lengthy testimony Monday, Minneapolis' police chief minced no words in condemning the actions of Derek Chauvin, the former officer who is charged with murder in the death of George Floyd.

Still, Arradondo's testimony was rare. That he was joined by a string of other law enforcement officers was remarkable and a sign that the so-called blue wall of silence is crumbling.

Paul Butler, a law professor at Georgetown University Law Center, said the blue wall means "that sometimes police officers close rank and — right or wrong — they're blue."

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