Also, the cop had his knee on the back of his neck. Your airway is in the front of your neck. You can place as much weight as you want on the back of your neck, it will not close off your airway. Try this, take a 6 foot piece of rope and tie a 50 pound weight to each end. Bend over at the waist, put the rope around your neck and lift it of the ground, tell me if you can still breath. I guarantee you can.