His bookkeeper is deaf.. That was the reason he got the job in the first place.
It was assumed that Enzo would hear nothing that he might have to testify about in court.
When the Godfather goes to confront Enzo about his missing $10 million, he takes along his lawyer who knows sign language.
The Godfather tells the lawyer, "Ask him where the 10 million bucks is that he embezzled from me."
The lawyer, using sign language, asks Enzo where the money is..
Enzo signs back, "I don't know what you are talking about."
The lawyer tells the Godfather, "He says he doesn't know what you are talking about."
The Godfather pulls out a pistol, puts it to Enzo's temple and says, "Ask him again!"
The lawyer signs to Enzo, "He'll kill you if you don't tell him." Enzo signsback, "OK. You win!
The money is in a brown briefcase, buried behind the shed in my cousin Bruno's backyard in Woodbridge !"
The Godfather asks the lawyer, "What did he say?" The lawyer replies, "He says you don't have the balls to pull the trigger."