Wow David, I never thought of that.A stunned mouse/rat could regain consciousness while the snake is swallowing it or while the snake is not on its guard and tear the poor snake to pieces from the inside. Make 100% SURE that the prey is dead.
I always thought that when a snakes constricts, he constricts until death of the prey. Is that not correct? By looking at the prey after constriction and prior to eating, they are as flat as a pancake, I can't imaging it ever coming back to life.