and could clearly breathe well enough to keep proclaiming that he couldn't breathe.

lol!

This is nonsensical. He's speaking quite voluminously while Chauvin is on top of him. His knee wasn't on either of his carotid arteries to cause him to pass out. I have little doubt that he died from lack of oxygen, however, it clearly wasn't from the knee.

https://www.youtube.com/watch?v=NcFoi1q9Cf4

From your NPR link

"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.

Again, this is nonsensical as he clearly had no problem being loud despite the knee on his neck.

There's more than enough confounders for reasonable doubt to exist:

• the fentanyl - 4-5x a known lethal concentration, see my other post.

• his health

On cross-examination, defense attorney Eric Nelson honed in on Floyd's pre-existing cardiovascular disease, pointing out that Floyd had a 90% blockage of the right coronary artery.

• his untreated hypertension (high blood pressure) that got as bad as 216 over 160. For reference, 120/80 is considered normal. His heart literally had to work twice at least twice as hard to pump his blood.

Floyd’s blood pressure, 216 over 160, came as a surprising figure to Fowler, a former Maryland chief medical examiner, in analyzing the case, he told Nelson.

• his oxygen saturation at 98%

Tobin testified that tests on Floyd's blood indicated his oxygen saturation level was 98 percent, meaning the amount of carbon monoxide would be no more than 2 percent.

Many of these people gave testimony the defies common sense as well medical knowledge, one expert cardiologist testifying on behalf of the prosecution:

https://www.unz.com/article/the-derek-chauvin-trial/

Dr. Rich said the medical records showed hypertension (high blood pressure), drug taking, and anxiety.

The doctor thought Floyd had a “strong” heart because of his high blood pressure. He said high blood pressure is bad for you over the long run, because the heart eventually “tires out.”

On cross-exam, Mr. Nelson asked Dr. Rich if, hypothetically, a patient with a 90 percent artery blockage can die of a heart attack and the doctor agreed. He agreed that Floyd had heart disease, but repeated that he did not think Floyd had a heart attack. He said his body had created extra blood vessels to compensate for the blockage, and added that a patient is more likely to have a heart attack with less than 90 percent blockage.