John 18:20

Jesus answered him, I have spoken openly to the world; I ever taught in synagogues, and in the temple, where all the Jews come together; and in secret I spake nothing.

Jesus well knew that the wily old hypocrite, Annas, was merely on a fishing expedition and quite properly refused to tell him anything. Besides that, Annas was not the legal high priest; and Jesus had already decided to make his formal testimony concerning his Messiahship before the Sanhedrin in formal assembly. In addition, the Pharisees' spies had been following Jesus diligently for months; and everything that Jesus had publicly stated was, in all probability, already known to Annas, as was also Caiaphas' determination to put Jesus to death.