As an old and retired medic, the lack of respiration and pulse doesn’t mean you are dead-dead. On the scale of "Not Dead to Dead-Dead, a lack of respiration’s and pulse means you are at the maybe dead on the line. And other factors will make the final determination about if you are actually dead or not.
The first determining factor in figuring out where the patient is on the scale, is if you make it into my amp-a-lamps or not. If you do, you are alive at least for a little while longer and I’mma let the doctor sort it all out for you. If you don’t make it in the back of my bus, then you are dead-dead and nothing can change that-- not even god himself.
No it’s not. It only becomes a criteria when you can no longer reasonably be sure that it can’t be restarted.
Source: Retired medic that has pronounced my share of dead people AND restarted a few hearts also.