In my opinion Arkie is right on both counts, from reading the Gospels there is no implication at any but those described in the narrative were culpable and Pilate, while responsible for the act in that he could have prevented it if he were determined to do so, was obviously not among those screaming for Jesus' blood. Certianly he was only involved in the process at the end and was not instrumental in bringing the charges which lead to the execution.

As far as the law is concerned, as governor for the region, Pilate had close to absolute discretion in the region only tempered by the occasional order from Rome and his desire to keep the peace over his local subjects. It is my opinion that he did not involve himself as an advocate for Jesus because it was politically expedient and also because jesus did not as him to intervene.