And that's not difficult here. Chauvin caused the death. I don't see a reasonable way that putting ones body weight on an unconscious man who has no pulse
didn't contribute to the death. And then the rest is plain and obvious, other than the felony, but I could see a felony conviction too.
Though as
@LordSunhawk says, the prosecution could easily fuck this up.
Once he's unconscious, it
is illegal (regardless of protocols), because the man cannot resist and there is a duty of care to an arrested person. Also, a strong person like Crowder not having problems breathing really doesn't apply to what Floyd went through. Crowder also found no problem with waterboarding through his 'test', even though that definitely is torture, as a number of people who experimented with it found, so I don't trust his test controls. Third, stopping the ribs from expanding certainly does affect ones ability to breathe.