We can immediately tell that A is not the knight and C is not the knave. If B is not the spy, or if spies are constrained to statements that are either true or false, then B's statement cannot be first. Amusingly, in all six cases the outcome is the same. We can't tell. Thus, the spy cannot be pinned down as A, B, or C, nor as the person C pointed to, nor the one C didn't point to.
Spy can be any.
Since the judge already knew that C was not the spy, the answer pattern must have been b or d. Since we can't tell the difference between cases 2 and 3, we can't even tell whether the judge is a spy. I will also assume that A, B, and C all answer either yes or no, as directed by the judge. The judge makes a conviction and the trial stops. Refer to the tables in question 6 for the state after B's answer.