Video report by ITV News Correspondent Robert Moore
George Floyd died due to a lack of oxygen caused by being pinned facedown with his hands cuffed behind him, a medical expert said at former police officer Derek Chauvin’s murder trial.
Mr Floyd could not take in enough oxygen while he was being held down on the pavement by Chauvin and other officers and this led to damage in his brain and an abnormal heart rhythm that made his heart stop, said Dr Martin Tobin.
The lung and critical care specialist at the Edward Hines, Jr VA Hospital and Loyola University’s medical school in Chicago supported the prosecutors' claim that it was Chauvin's actions, not Mr Floyd's illegal drug use and underlying health conditions, that killed the 46-year-old black man last May.
The expert analysed a graphic presentation of the three officers pinning down Mr Floyd and said Chauvin's knee was "virtually on the neck for the vast majority of time".
He added it was “more than 90% of the time in my calculations”.
He said it appeared Mr Floyd was getting enough oxygen for the first five minutes to keep his brain alive because he was still speaking.
But he explained that as the space in the airway narrows, breathing becomes "enormously more difficult", saying it would be worse than “breathing through a drinking straw”.
He said 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”.
When Mr Floyd’s head was face down, Dr Tobin said a ligament at the back of his neck would have protected his airway.
But with his head turned to one side, Chauvin’s weight would have compressed the hypopharynx.
The expert calculated that at times when Chauvin had his toes off the ground, half of his body weight, 41.5kg, was on Mr Floyd’s neck.
Dr Tobin pointed out that Officer J Kueng held Mr Floyd’s left hand upward, and Chauvin’s right knee was on Mr Floyd’s side, meaning “the ability to expand his left side is enormously impaired.”
The handcuffs and the hard surface also made it harder for Mr Floyd to breathe, he said.
At one point, the medical expert invited jurors to examine their own necks to better understand the effect of a knee on a person's neck. Most of the jurors felt their necks, although the judge later told them they did not have to do so.
Ex-police officer Chauvin, 45, is charged with murder and manslaughter of Mr Floyd on May 25.
Mr Floyd was arrested outside Cup Foods store after he allegedly tried to give a shop worker a counterfeit $20 note.
Video shows Mr Floyd struggling and claiming to be claustrophobic as police tried to put him in a car. They then pin him to the pavement. Mr Floyd could be seen crying that he could not breathe as members of the public yelled at Chauvin to get off him.
Defence lawyer Eric Nelson argued that Chauvin “did exactly what he had been trained to do over his 19-year career”, and that other factors, including drugs, killed Mr Floyd.
Fentanyl and methamphetamine were found in Mr Floyd’s system.
The trial continues.