Lack of oxygen from police restraint killed George Floyd, doctor testifies at Chauvin murder trial

Chicago-based breathing expert Martin Tobin answers questions during the ninth day of the trial. PHOTO: REUTERS

MINNEAPOLIS (REUTERS) - Two medical experts used anatomical diagrams and charts to testify on Thursday (April 8) that George Floyd was killed by police pinning him to the ground, not a drug overdose, undermining a key assertion by former police officer Derek Chauvin in his murder trial for Floyd's deadly arrest.

Dr Martin Tobin, who treats patients in a Chicago hospital's intensive care unit, told the jury that Floyd died "from a low level of oxygen" caused by being handcuffed face down in the street with the police officer's knee on his neck.

Video of the arrest last May sparked global protests.

Tobin said any "healthy person" would have died in a similar restraint, which he compared to a vice, confirming the county medical examiner's finding that Floyd's death was a homicide at the hands of police.

A second doctor said the toxicology tests he performed on Floyd's blood found levels of fentanyl that were comparable to those found in samples taken from living people detained for driving under the influence of narcotics.

Video of the arrest showed Chauvin, who is white, pinning Floyd's neck to the ground with his knees for more than nine minutes as Floyd, a 46-year-old black man, begged for his life, gasping more than two dozen times: "I can't breathe."

Chauvin has pleaded not guilty to murder and manslaughter charges.

Here are important moments from the ninth day of witness testimony:

Dr Daniel Isenschmid, toxicologist who tested Floyd blood samples

Isenschmid said the amount of methamphetamine in samples of blood taken after Floyd's death, 19 nanograms per milliliter, was similar to levels a doctor would expect to see in a patient after taking a single dose of the drug in a prescribed form for attention-deficit disorder.

He said the concentration of fentanyl in Floyd's blood was 11ng/ml, and there was evidence a lot of the opioid had been broken down in Floyd's body to norfentanyl, which a doctor would not expect to see in someone killed rapidly in an overdose.

Isenschmid also compiled data from his office on samples taken from 2,345 people stopped for driving under the influence in 2020, noting that people addicted to opioids need to take higher doses as tolerance builds up. The average level of fentanyl found in the blood of those people, all of whom were alive, was 9.69ng/ml, he said.

Dr Martin Tobin, expert in the respiratory system

Tobin said Floyd's breathing became fatally shallow under the police restraint but that the number of breaths he took per minute did not decrease up until the moment he lost consciousness, contradicting a defence theory.

Tobin said that a fentanyl overdose, in contrast, is marked by a sharp decrease in the frequency of breaths.

The shallow breaths resulted from a combination of measures applied by police, including placing Floyd prone on the street, handcuffing his hands behind his back and the officer kneeling on his back and neck, he said.

A portrait of George Floyd sits in a ring of flowers at the memorial site known as George Floyd Square on April 8, 2021 in Minneapolis, Minnesota. PHOTO: AFP

Tobin unbuttoned his shirt collar at one point and most jurors followed his request to do the same as he felt his neck, describing how Chauvin's knee compressed the delicate tissue of the hypopharynx, blocking that part of the respiratory system in the lower part of the throat.

Tobin calculated that at times, Chauvin, who suspected Floyd of passing a fake US$20 bill, was exerting 91.5 pounds (41.5kg) of downward pressure on Floyd's neck.

Tobin discussed frames from the video that he said showed Floyd trying to push his chest up from the street using his fingers and his face as leverage as he struggled for breath beneath Chauvin and three other officers.

"They're pushing the handcuffs into his back and pushing them high, then on the other side you have the street. The street is playing the crucial part," Tobin said. "It's like the left side is in a vice."

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Chauvin can be heard on video dismissing Floyd's pleas by saying: "It takes a heck of a lot of oxygen to say things."

Tobin called that a "dangerous mantra."

"It's a true statement, but it gives you an enormous false sense of security," Tobin said. "Certainly at the moment you're speaking, you are breathing, but it doesn't tell you if you're going to be breathing five seconds later."

Tobin said Floyd's leg could be seen jumping up in an involuntary seizure as his brain was starved of oxygen.

Soon after, Tobin said, the moment came when Floyd did not have even "an ounce of oxygen left in his entire body," although Chauvin's knee stayed on Floyd's neck for three more minutes.

In cross-examination, Eric Nelson, Chauvin's lead lawyer, asked Tobin if he had personally weighed Chauvin, who in police reports is recorded as 140 pounds (63.5kg), or Chauvin's equipment in order to calculate the pressure applied by the officer's knee. Tobin said he had not.

Nelson sought to get Tobin to say Floyd's death could have been caused by fentanyl, but Tobin said medical evidence contradicted that.

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