John 18:30

30. If… not a malefactor Uttered in a sarcastic tone, this reply would be of a very irritating character. Uttered, however, in a tone of courteous sauvity, it apologizes for troubling Pilate, assuring him that nothing but the fact that they had a malefactor could have brought them there.

Their real purpose, under either meaning, is to precipitate Pilate into the slaying of Jesus. They first wished to do this, if possible, by making Pilate execute him in implicit compliance with their judgment. Or, failing in that, they will accuse Jesus of treason, and induce Pilate to condemn and crucify. And failing in that, they will boldly threaten Pilate himself, and compel him to execute whether he condemn or not. Pilate, after availing himself of every possible subterfuge, finally yields to their last master-stroke.