I know exactly how fast someone can be put out, I also know plenty of people who think they are hard enough and resist tapping out until they can't. The position of the officers knee would make it impossible to block both the arteries and airway. I could possibly see the pressure on the back of his neck maybe causing increased pressure on his voice box, but is it enough to make someone suffocate that isn't high as a kite. That is what the jury need to decide.
You know when you are teaching new white belts how to shrimp, and you go knee on belly and transition from side to side? You ever notice how exhausted they are? That’s because your knee is stopping them from breathing properly.