George Floyd ‘died from a low level of oxygen’ and had 90lbs of weight on his neck, doctor testifies

George Floyd died because his lungs weren’t able to get enough air, impairing the brain and causing his heart to stop, a lung expert testified in the Derek Chauvin murder trial on Thursday.

“Mr Floyd died from a low level of oxygen,” testified Dr Martin Tobin, a lung expert and ICU doctor from Loyola University called by the state. “The cause of the low level of oxygen was shallow breathing, small breaths, small tidal volume, shallow breaths that weren’t able to carry the air through his lungs.”

Confirming the cause of Mr Floyd’s death is a central question in the case. The state of Minnesota argues former Minneapolis police officer Chauvin smothered Mr Floyd to death when he kept his knee on his neck for nine minutes during an arrest last May for a counterfeit $20 bill. The defence, meanwhile, suggests a drug overdose and Mr Floyd’s pre-existing heart condition was responsible.

Mr Tobin said four factors caused this lack of oxygen: Mr Floyd was in prone position, he was in handcuffs against hard pavement, there was a knee on his neck, and that there was a knee on his back. Together these forces cut off practically all function in his left lung, according to Mr Tobin.

“Basically on the left side of his lung, it was almost like a surgical pneumonectomy. It was almost like a surgeon had gone in and removed the lung,” the lung expert said. “It’s like the left side is in a vice. It’s totally being totally pushed in, squeezed in from each side,” he added.

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In addition to compressing Mr Floyd’s lungs, Mr Chauvin also reduced the amount of air that could come in through a passage in the bottom of the throat called the hypopharynx by kneeling on Mr Floyd’s neck, the lung doctor testified. According to the doctor’s testimony, Mr Chauvin had an estimated ninety pounds of pressure on Mr Floyd’s neck at times.

Mr Tobin also suggested that Mr Floyd may have suffered a brain injury about five minutes into police kneeling on top of him, at which point Mr Floyd began ceasing to speak and cry out.

“You can’t speak without a brain being active, so we know there’s oxygen getting to his brain whenever he is making an attempt to speak,” Dr Tobin said.

Among the most important parts of his testimony were his thoughts about whether Mr Floyd showed signs of dying from drug-related factors. The defence has argued drugs, rather than Mr Chauvin’s knee being pressed into Mr Floyd’s neck for more than nine minutes during the arrest, caused the death.

But according to Dr Tobin, fentanyl in Mr Floyd’s body at the time didn’t play a role in slowing his breathing before he ultimately died. Fentanyl, Mr Tobin explained, is a powerful opioid that can slow the breathing rate, but Mr Floyd continued to take breaths at a normal clip before passing out about five minutes into his detention on the ground.

“It tells you that there isn’t fentanyl on board that is affecting his respiratory centres,” Dr Tobin said. (Mr Tobin did not perform an autopsy of Mr Floyd and based his opinions instead on clinical experience. The county medical examiner is slated to testify on Friday).

Up until now, the trial has largely focused on police training, and what amount of force is legal and reasonable to use in given situations. A number of use of force experts and high-level Minneapolis police officers, including the police chief, have condemned Mr Chauvin’s actions as unlawful and unnecessary.

Now the trial is moving to focus more on medical evidence, with the county medical examiner who conduct an autopsy on Mr Floyd slated to testify on Friday.