What does John 18:30 mean?

The statement here seems obvious, but does nothing to answer the question Pilate has asked (John 18:29). This reflects the mutual disrespect between Jewish leaders and the Roman governor. Not only did Pilate rule on behalf of a conquering Roman Empire, but he was also known for being cruelly violent. This remark is a not-so-subtle way for the scribes and Pharisees to imply that they, not Pilate, are the legitimate judges of guilt or innocence. They would not have stooped to consulting with a Gentile unless there was no other choice. Pilate's dismissive response (John 18:31) corresponds with what he already knows: that Jesus is being targeted out of jealousy, not an actual crime (Matthew 27:18).

As he often does, John omits details clearly given in other Gospels, focusing instead on his unique message. Using an artificial mob, the scribes and Pharisees will insist that Jesus' claims are rebellion against the Roman Empire (Matthew 27:24), and imply that there will be civil unrest if Jesus is not executed (John 19:12–15). In this passage, John moves quickly to explain that Jesus' enemies are seeking the death penalty (John 11:49–53; 18:31), setting up Pilate's fascinating private conversation with Christ (John 18:33).