Derek Chauvin trial: Medical expert testifies George Floyd died of ‘low level of oxygen’

George Floyd died from a lack of oxygen which damaged his brain and caused his heart to stop when he was pinned down by Derek Chauvin, a medical expert has told the former police officer’s murder trial.

Mr Floyd’s breathing was too shallow to take in enough oxygen while he was pinned facedown with his hands cuffed behind his back for nine and a half minutes as Chauvin knelt on his neck and back, Dr Martin Tobin said.

Dr Tobin is a lung and critical care specialist at the Edward Hines, Jr. VA Hospital and Loyola University’s medical school in Chicago.

He took the stand as part of an effort by prosecutors to establish that it was Chauvin’s actions - not Mr Floyd’s drug use and underlying health conditions, as the defense contends - that killed the 46-year-old Black man last May.

Tobin, analyzing a graphic presentation of the three officers pinning Floyd for what prosecutors say was almost 9 1/2 minutes, said Chauvin’s knee was “virtually on the neck for the vast majority of time.”

He said it was “more than 90% of the time in my calculations.”

He said it appeared that Floyd was getting enough oxygen for about the first five minutes to keep his brain alive because he was still speaking.

But Tobin explained to jurors what happens as the space in the airway narrows, saying breathing then becomes “enormously more difficult,” adding that it would be worse than “breathing through a drinking straw.”

Tobin testified that if the hypopharynx - the bottom part of the throat - becomes totally obstructed, it takes just seconds to reduce the level of oxygen to where it would result “in either a seizure or a heart attack.”

Prosecutors showed images of Floyd side by side, one with the front of his face smashed against the pavement and another with his head turned. Tobin said that when Floyd’s head was facedown, a ligament at the back of his neck would have protected his airway. But with his head turned, Chauvin’s weight would have compressed the hypopharynx.

The expert calculated that at times when Chauvin was in a near-vertical position, with his toes off the ground, half of Chauvin’s body weight - 91.5 pounds - was directly on Floyd’s neck.

Tobin said other factors worsened the effect on Floyd: He pointed out that Officer J. Kueng held Floyd’s left hand upward, and Chauvin’s right knee compressed Floyd’s side, meaning “the ability to expand his left side is enormously impaired.” The handcuffs and the hard surface also interfered with Floyd’s ability to breathe, Tobin said.