So from reading the rules and rereading them I had come to the conclusion that when you inflict multiple crits. So as far as I understand it when you inflict a critcal injury the recipient rolls Fitness reduces it from 5 down to 3.
person receives another crit with deadliness 5 only reduces it by 1 receiving 4. this compounds onto the 3 they had before making the total 7.
is this correct because it's the only one that makes sense as to how you would be able to potentially kill someone during a fight outside of a coup de gras.