"Behold the man!" Pilate shouts to the crowd who has turned Jesus over to him. This Galilean is clearly innocent. But Pilate fears the rabble - if he refuses to condemn Christ, it will be proclaimed that he, the Roman Governor, is "no friend of Caesar's." If he does condemn him, he fears this man's followers may revolt. Pilate sees this in many respects as a lose/lose for him.
The crowd shouts all the louder: "Crucify him! Crucify him!" And all the while the prisoner's words keep confounding him: "Everyone who belongs to the truth listens to my voice" (John 18:37). Who is this man? Where does he come from? Where is this kingdom of his, the kingdom he claims is "not of this world?"
Pilate has seen something in those eyes that he cannot comprehend - something he ultimately refuses to face. He is too weak to do the right thing, too weak to act justly. This sham trial and wholesale condemnation is something he chooses to step away from rather than settle himself.
The basin is brought to him. He ceremoniously washes his hands before the mob and then says those infamous words: "I am innocent of this man's blood, look to it yourselves" (Matthew 27:24).
Thus Pilate hands the most innocent one of all, the spotless victim, the unblemished Lamb of God over to the slaughter.