The trial against Jesus is the best attested incident from Pilate's career. We have four independent reports: the Jewish Antiquities by Flavius Josephus (below), Mark's gospel, John's gospel and the Annals of the Roman historian Tacitus. The passion narratives of Matthew and Luke are derived from Mark's, but contain extra information that may be authentic.
At first sight, is is strange that the Jewish leaders handed Jesus over to Pilate to have him executed. Of course, the carpenter from Galilee had predicted the coming Kingdom of God, and he had - in a fit of temper - overturned the banks of the money changers and the benches of those selling doves, calling the sanctuary "a den of robbers". This was a serious misdemeanor but insufficient to have a man executed.
The real reason why Caiaphas wanted to get rid of the man from Nazareth was - probably - that he had claimed to be "the Son of Man sitting at the right hand of the Mighty One and coming on the clouds of Heaven," which meant that Jesus was to share God's throne and to judge the Temple authorities. The high priest considered this blasphemy.
Pilate was less interested in a blasphemer, and therefore Caiaphas presented him a different case: Jesus had claimed to be the "King of the Jews". In other words, he was charged with high treason. Although we learn about this from the sometimes biased gospels, we must consider this a historical fact, because it is too embarrassing to have been invented.
Caiaphas could charge Jesus with high treason because some of his disciples considered him the Messiah, an identification to which Jesus seems to have responded ambiguously.
Unfortunately, there were many messianologies. Some thought that the Messiah was a military leader who was to defeat the Romans; others agreed that the Messiah was to restore Israel, but preferred a moral revival inaugurated by a sage explaining Moses' law. All these messianologies used titles like "king" and "son of David"; most of them predicted that the twelve tribes would be re-established; many assumed that the Messiah's ministry would bring about God's personal rule of this world (the "Kingdom of God"). The many similarities made it easy to confuse these messianologies.
It is probable that Jesus considered himself a prophet and a teacher, but it must have been easy for Caiaphas to interpret Jesus' action against the Temple in a military way. He had been arrested after a riot, was called "king Messiah", claimed to be a descendant of David, had twelve disciples, had announced the destruction of the Temple, and had threatened to judge the high priest, stating that he was God's personal representative. Pilate had to crucify this would-be king. If he did not execute the pretender, he had failed as a governor.
According to the gospels, the governor sensed that Caiaphas' interpretation of the claim that Jesus was the Messiah was biased ("for he knew that the chief priests had handed him over because of envy"note[Mark 15.10.]). There is a possibility that this is confirmed by Flavius Josephus, who writes:
At this time there appeared Jesus, a wise man. For he was a doer of startling deeds, a teacher of the people who receive the truth with pleasure. And he gained a following both among many Jews and among many of Greek origin. And when Pilate, because of an accusation made by the leading men among us, condemned him to the cross, those who had loved him previously did not cease to do so. And up until this very day the tribe of Christians, named after him, has not died out.note[Jewish Antiquities 18.63-64. Go here for a discussion of the precise wording of this text, which is known as the "Testimonium Flavianum".]
This is a strange description of the case. Any straightforward report would have told that Pilate had ordered the man from Nazareth to be executed because he had committed this or that crime. But instead of naming the accusation, Flavius Josephus mentions the accusers. This is all the more remarkable because the Jewish historian detested the would-be kings and protesters he held responsible for the great war between the Jews and Romans of 66-70, and usually delights in writing about their deserved punishment. The fact that he now refrains from telling about the charge of high treason strongly suggests that he considered it to be a false accusation; and the fact that Flavius Josephus explicitly mentions the Jewish leaders may suggest that his source told him that Pilate had refused to accept the sole responsibility.
However we may read the testimony of Flavius Josephus, at least the gospels assume that Pilate was not convinced that the carpenter from Nazareth was guilty. Both Mark and John - independent sources - show us how the governor forced the Jews to take a part of the responsibility: Pilate declares that he cannot find fault in Jesus and repeatedly refers to Jesus as "your king" - thereby pushing the Jerusalem populace into declaring that they want the man from Galilee crucified.
According to Matthew (whose report cannot be corroborated) Pilate even washed his hands: a Pharisean custom to wash away impurity, such as the impurity caused by convicting an innocent man.
Of course, this was nonsense. As the supreme magistrate of Judaea, Pilate carried the full responsibility. But it is not implausible that the governor used the occasion to obtain pledges of loyalty from his subjects. John's statement that the Jews even declared to have "no king but Caesar" may indeed be a historical fact. Pilate may have regretted that he had to crucify a man who was fairly innocent, but he may have considered this human sacrifice an acceptable price to be paid for the smooth cooperation with the Temple authorities.
Although it is possible that the governor wanted to lay the responsibility with the Jews, he was not looking for a conflict with his subjects. The gospels mention several instances where Pilate shows respect for their customs. According to Matthew 27.24, he washed his hands; according to John 18.29 he allowed Jesus' opponents to speak from without his headquarters, the Praetorium (entering a pagan building would defile the Jewish priests); and Mark 15.43 and John 19.38 state that he allowed Joseph of Arimathea to bury the dead man before the beginning of the sabbath. (Since they state this independently, this has to be authentic.)
The latter story is very remarkable: the emperor Augustus' directive that those who had suffered the death penalty were allowed a decent burial, did not pertain to those executed on a charge of high treason. As a matter of fact, it was almost proverbial that the crucified were the prey of dogs and a feast for birds. Pilate's permission to have Jesus buried and (according to John 19.39) regally embalmed, is the act of a governor anxious to respect the religious feelings of the Jews.
It should also be noted that Pilate did not round up the other suspects, although it must have been possible to demand the angry Jerusalem populace to help search for people speaking with a Galilean tongue. If Pilate really believed that the Galileans had stormed the Temple and wanted to establish the Kingdom of God by violent means, this was almost irresponsible. This fact - Mark, John and Flavius Josephus confirm that Jesus was the only Galilean executed - almost proves that Pilate did not believe that Jesus was a political Messiah. In an age when executions were used as deterrents, his behavior suggests dislike for excessive violence.
On the other hand, he had condemned an almost innocent man to a brutal, slow, and extremely painful death. On the same day, Pilate released a man named Barabbas who had been arrested after a riot which had cost some deaths. The narratives of Mark and John, which state that it was Pilate's custom to free a prisoner at Passover, cannot be taken at face value: the idea of a yearly release of murderers is ridiculous. Besides, their stories are colored by Christian theology and apology: Barabbas is presented as the first to be saved by Jesus' passion, and the Jews rather than Pilate demand Jesus' death.
However, the release of this man is twice attested, and is quite probable. Nevertheless, it must be stressed that there is an interesting parallel to the choice of the scapegoat at the Day of Atonement as described in Leviticus 16.7-10: two goats are selected, and the lot decides which one is chosen to be sacrificed as a sin offering, while the other will be released into the wilderness. The parallel with the story of Barabbas and Jesus is remarkable.
The irony of the release of Barabbas - whether this was a historical fact or not - was not lost on the first Christians: a guilty man had been released, an innocent man had been killed.