"'Are you the king of the Jews?' asked Pilate. 'You have said so,' Jesus replied. The chief priests accused him of many things. So again Pilate asked him, 'Aren't you going to answer? See how many things they are accusing you of.' But Jesus still made no reply, and Pilate was amazed." NIV translation
We see that, instead of the charge of blasphemy, the Sanhedrin charged Jesus with treason against the Romans by saying that He was the "king of the Jews". Pontius Pilate was a politician and, as it always is with politicians, they are consumed with retaining their power and position. So, Pilate asked Jesus if the charge was true and Jesus did not directly say yes or no and refused to answer the accusations that were made against Him. We see that "Pilate was amazed" by the fact that Jesus did not defend Himself like a normal prisoner. Surely, Pilate was used to men begging him to spare their lives but Jesus did not even utter a word. He could have easily opened His mouth and proved that the charges were false but, in keeping quiet, Jesus was remaining focused on the will of the Father. The prophet Isaiah had foretold the fact that the Messiah would not cry out even as He was being afflicted and oppressed (see Isaiah 53:7). Even as He was facing death, Jesus held true to the word of God as given by the prophets.