Expert’s testimony on how George Floyd died
Doctor testifies healthy person would have died
A doctor said a healthy person in the same situation would have died.
MINNEAPOLIS – A physician with 40 years of experience in the physiology of breathing offered critical testimony in Derek Chauvin’s murder trial Thursday, describing why George Floyd couldn’t breathe while Chauvin and other officers held him facedown and handcuffed on the street last Memorial Day.
Dr. Martin Tobin took jurors through the repercussions of the officers’ use of force that, he testified, slowly suffocated him. After Floyd was pulled from a police cruiser, he was placed on his stomach on hard asphalt. His hands were handcuffed behind his back, and officers cranked his arms up against his body, putting pressure against his chest. And Chauvin’s left knee was on Floyd’s neck while his right was on Floyd’s back and side, Tobin said, compressing Floyd’s lungs even more.
“It’s like the left side (of Floyd’s body) is in a vise. It’s totally pushed in, squeezed in from the street at the bottom,” Tobin said. “And then, from the way the handcuffs are manipulated, that totally interferes with central features of how we breathe.”
Tobin told jurors that “a healthy person subjected to what Mr. Floyd was subjected to would have died as a result,” potentially undercutting the defense’s argument that Floyd died from a combination of his struggle with officers, health conditions and drugs.
His testimony came on the ninth day of the trial after prosecutors had presented video evidence captured by officers’ body-worn cameras and bystanders, as well as the testimony of eyewitnesses, Minneapolis police officials, paramedics, an emergency room doctor, and an expert in the use of force.
Testimony of medical experts is likely key in the trial of Chauvin, is charged with second- and third-degree murder and second-degree manslaughter.
‘Trying to breathe with his fingers’
Tobin said the actions by Chauvin and two other officers, J. Alexander Kueng and Thomas Lane, compressed Floyd’s airway and forced him to take shallow breaths. Over time, Tobin said, Floyd’s oxygen level dropped to the point that it led to a seizure. He said Floyd’s cause of death was lack of oxygen, which also caused brain damage and an abnormal heartbeat.
Tobin said he watched videos of Floyd’s arrests “hundreds of times” and calculated that Chauvin’s left knee was on Floyd’s neck for the majority of the 9 minutes and 29 seconds he was restrained on the ground.
The effect of the officers’ actions and Floyd’s position was almost “as if a surgeon had gone in and removed the lung,” Tobin said, referring to Floyd’s left lung.
Tobin said images from the videos show Floyd trying to use his right fingers and knuckles to raise the right side of his chest to get air into his lungs. “This tells you he has used up his resources and he’s literally trying to breathe with his fingers and knuckles,” Tobin said.
Some of the jurors sat up and took notes when Tobin said a healthy person would have died if they were restrained like Floyd was.
90 pounds of pressure
Floyd’s position restricted a part of the airway called the hypopharynx, which is vulnerable because it is so narrow, Tobin said. As Chauvin pressed his knee into Floyd’s hypopharynx area, Tobin said, it became harder for Floyd to breathe than it would have been if he been inhaling through a drinking straw.
Tobin testified about an image from a video showing the toe of Chauvin’s left boot lifted off the ground as he kneeled on Floyd. At that point, Tobin testified, 91.5 pounds were pressed directly onto Floyd’s neck. Even when Chauvin’s toes were on the ground, he said Floyd had 86.9 pounds on his neck.
Tobin said Floyd’s lung capacity dropped by nearly a quarter when he was placed in the prone position. Once Chauvin pressed his knee onto Floyd’s neck, his lung capacity dropped again, for a total reduction of 43%, Tobin said.
“Now the work Mr. Floyd has to perform is huge,” Tobin said. “With each breath, he has to fight against the street, fight with the small volumes he has, and try to lift up the officer’s knee with each breath, and has to also lift up the effect of the officer pumping up his arm – the handcuffed arm.”
Defense attorney Eric Nelson tried to discredit Tobin’s calculations by questioning the assumptions about Floyd’s health and Chauvin’s weight. Tobin said he made “very few assumptions.” Nelson noted that an autopsy showed that Floyd’s hypopharynx was not damaged, nor was his neck bruised. Tobin said he “wouldn’t expect there to be anything found” because oxygen deprivation doesn’t leave a fingerprint.
Floyd cried out, “I can’t breathe” more than 20 times. Officers can be heard saying on video that if he could talk, he could breathe. Tobin said that is a “dangerous” assumption because it doesn’t mean someone still will be breathing in the next moment. Being able to speak meant Floyd’s brain was functioning, Tobin said, and it meant he did respirate the moment before.
A normal trachea has a diameter between the size of a quarter and a dime, Tobin said. When the trachea is restricted to 15% of that, he said, “you are still able to speak.”
Tobin said he reviewed Floyd’s medical records and saw that a toxicology report found fentanyl and methamphetamine in his system. He said Floyd’s medical conditions and drug ingestion were not relevant to his death.
Floyd’s average rate of respiration would have been faster if he were suffering from the symptoms of heart disease, Tobin said. He calculated that Floyd’s breathing rate was the same as a healthy person, even though fentanyl typically represses breathing.
The significant increase in Floyd’s carbon dioxide levels as measured by paramedics and hospital emergency room doctors is “completely explained” by the lack of oxygen that Floyd suffered from the restraint, Tobin said.
Tobin calculated that Floyd was able to speak during the first 4 minutes and 51 seconds that he was on the ground under the officers. That meant oxygen was still reaching his brain. Tobin testified that the video then showed Floyd struggling to create an area for oxygen to enter his lungs, lifting his right shoulder up and down to expand the lung space, and rocking his hips and spine. At 5 minutes and 3 seconds, Floyd kicked out one leg, which signaled he had suffered a seizure from the lack of oxygen, Tobin said.
After that, Tobin said, the placement of Chauvin’s knee was no longer relevant because he had already sustained a massive brain injury.