Derek Chauvin has been charged with second-degree murder and manslaughter in the death of George Floyd, but another former officer involved, J. Alexnder Kueng, held a knee into Floyd’s back, which has some calling into question as to whether or not it contributed to Floyd’s death.

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“There are three mechanisms by which we breathe that can be obstructed that can cause death, obstruction to the nose and mouth, compression the neck or compression of the back. All three were operative here, the pressure on the neck prevents blood flow, impairs blood flow to the brain, which has oxygen in it. It impairs breathing and air into the windpipe and trachea and into the lungs, which diminishes the oxygen going to the blood," Dr. Michael Baden, the forensic pathologist who performed the independent autopsy on Floyd, told Fox News.

Thomas Lane, 37, Tou Thao, 34, and J. Alexander Kueng, 26, were charged with aiding and abetting second-degree murder and aiding and abetting second-degree manslaughter.

The roles of the other former officers involved, particularly the officer who held a knee into George Floyd’s back, have come into question as to whether or not any of their direct actions could have been contributing factors in Floyd’s death. According to Dr. Baden, when the officer's knee was pushed into Floyd's back it could have constrained the diaphragm, preventing the body from inhaling and therefore making it difficult, if not impossible, to breathe.

“In order to inhale and exhale the diaphragm contracts and relaxes, when it contracts, it pulls the lungs down the chest. To inhale and exhale the diaphragm, it has to go up and down, normally about 10 to 12 times a minute. When there is pressure on the back, that grip prevents the diaphragm from moving when a person is in the prone position. And that's why Floyd said, ‘I can't breathe. I can't breathe,’ because he couldn't inhale," said Baden.

Baden said police are under a "false impression” that if someone speaks that means they can breathe.

“Unfortunately, many police are under the impression that if somebody talks, they're breathing. That's not true,” he said.

In the video that lasted eight minutes and forty-six seconds, Floyd cries out, “I can’t breathe,” and with Floyd’s body being held down in the prone position, his “lungs weren’t getting enough oxygen,” according to Baden.

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“There's two things happening here. One, he couldn't inhale. Two, the lungs weren't getting oxygen from breathing in, and the blood vessels, the carotid arteries in particular, bringing blood to the brain didn't have much oxygen in them. And the blood flow to the brain was impaired. There's also marks on his nose and face that would indicate that at some point they were pressed against the ground, the roadway, which would impair breathing, too,” Baden explained.

“So that pressure on the back in the prone position can cause death because the person can't breathe. But pressure on the neck prevents the blood flow and airflow from going to the brain and into the lungs. And that alone can cause death. I have two things here that can cause death," Baden said. "The pressure on the back would have contributed and is the more likely kind of pressure that causes somebody to say, 'I can't breathe, I can't breathe' because they know they can't inhale."