What does Matthew 27:13 mean?

Pontius Pilate was no friend to the Jewish ruling council, the Sanhedrin. History depicts Pilate as harsh and cruel. He was reported not to like the Jewish people, in general. Prior to Jesus' arrival, he was associated with incidents of civil unrest prompted by his own arrogant insults of the Jewish people. Afterwards, he was removed from his position, apparently due to another such ugly scene. He recognizes the personal vendetta Jesus' enemies are pursuing (Matthew 27:18). He was not the kind of politician to condemn a prisoner just to satisfy a high priest. However, the fragility of his political position may have been known, and one reason the religious leaders have come with an agitated crowd (Matthew 27:24).

The question Pilate asks here is incredulous. The real meaning is "aren't you going to respond to this?" Pilate wants Jesus to answer. He has every reason to hear the other side of the story. The Jewish leaders were basically accusing Jesus of being a rebel who was trying to stir up the people to overthrow Rome. Jesus, though, did not have the look of that kind of man. He was calm, resolved, and silent.