Ok, can you explain what happened with Chauvins knee?

He used his knee to kill Floyd, that's what happened.

Just curious because the autopsy didn't find any damage to the neck commensurate with choking.

That sounds about right because Floyd did not die from choking.

Dr. Martin Tobin, a pulmonary specialist who works in critical care, testified Thursday that George Floyd died from a lack of oxygen, bolstering the prosecution's argument that former Minneapolis police officer Derek Chauvin caused Floyd's death last May.

"Mr. Floyd died from a low level of oxygen, and this caused damage to his brain that we see. And it also caused a PEA [pulseless electrical activity] arrhythmia that caused his heart to stop".

Four factors led to Floyd's low oxygen level, Tobin said:

• his prone position on the street;

• the handcuffs that pulled his arms back;

• a knee on his neck;

• a knee on his back and down his side.

"All of these four forces are ultimately going to result in the low tidal volume, which gives you the shallow breaths" that can't effectively bring oxygen into the lungs, Tobin said.

Chauvin's right knee seems to have alternated between resting on Floyd's back and on his arm and "rammed into Mr. Floyd's left chest," Tobin said. He said that both placements would have an "extremely similar" effect on someone's ability to breathe in the position Floyd was in.

Tobin told the jury that the officers made it harder for Floyd to breathe when they pushed the handcuffs into Floyd's back and raised his wrists higher as he lay on the street.

"It's like [Floyd's] left side is in a vise. It's totally being pushed in, squeezed in from each side," he said, clasping his hands tightly together to illustrate his point. The effect directly interfered with Floyd's ability to breathe and rendered his left lung almost entirely unable to operate, Tobin said.

As Floyd struggled to breathe, Tobin said, he eventually pressed his own forehead, nose and chin into the asphalt, attempting to "crank up" his chest to let air in. But as Floyd turned his head on its side, Tobin said, Chauvin's knee moved further toward the side of Floyd's neck, compressing his hypopharynx. Anyone experiencing that type of compression would find it "enormously more difficult to breathe," Tobin said.

As a courtroom display showed a still image of Chauvin holding his knee on Floyd, Tobin noted that the toe of the officer's boot was entirely off the ground. "This means that all of his body weight is being directed down at Mr. Floyd's neck," he said.

Tobin said he's aware that Floyd had preexisting medical conditions. But he concluded, "A healthy person subjected to what Mr. Floyd was subjected to would have died."

Just in case you deflect to fentanyl.

While Floyd's toxicology report did reveal fentanyl present, expert witnesses at his murder trial have stated there was not enough to be considered fatal or impact his breathing and oxygen levels. Floyd died due to lack of oxygen from the force of Chauvin's knee on his neck.