This book-keeper is deaf and it was considered an occupational benefit why he got the job in the first place, since it was assumed that a deaf book-keeper would not be able to hear anything and never have to testify in court.
When the Godfather goes to shake down the book-keeper about his missing $10 million bucks, he takes along his lawyer, who knows sign language.
The Godfather asks the book-keeper: "Where is the $10 million bucks you embezzled from me?"
The lawyer, using sign language, asks the book-keeper where the money is hidden.
The book-keeper signs back: "I don't know what you are talking about."
The lawyer tells the Godfather: "He says he doesn't know what you're talking about."
That's when the Godfather pulls out a 9mm pistol, puts it to the book-keeper's temple, cocks it up and says: "Ask him again!"
The attorney signs to the underling: "He'll kill you for sure if you don't tell him!"
The book-keeper signs back: "OK! You win! The money is in a brown briefcase, buried behind the shed in my cousin Enzo's backyard in Queens!"
The Godfather asks the lawyer: "Well, what'd he say?"
The lawyer replies: "He says you don't have the guts to pull the trigger!!"