Cutting off someone head with a knife like that? To lob off someone's head, executors need huge, sharp sword to provide enough force. Even then it required a great deal of skill to precisely swing and cut cleanly through the network of skin, membranes, muscles and spine. Butchering a chicken, cow or pig, especially a live one, takes a great amount of time and force. Using that knife to cut off someone's head cleanly is just impossible.