Canonically, noble team is known for their insane drinking habits. So at one of their parties, everyone was so wasted and Emile passed out on the couch. So Kat, being the brilliant person she is, decides to not use permanent marker on his visor, like most people, but rather carves on his visor with a knife. Now Kat is a light weight and she accidentally chopped off her arm while carving into his visor and then slipped again and chopped into Emile's throat and cut out his larynx accidentally inhibiting his ability to speak. I base this on absolute fact.