First thing in the morning, the chief priests, together with the elders and scribes and the rest of the Sanhedrin, had their plan ready. They had Jesus bound and took him away and handed him over to Pilate.
Pilate put to him this question, Are you the king of the Jews? He replied, It is you who say it. And the chief priests brought many accusations against him. Pilate questioned him again, Have you no reply at all? See how many accusations they are bringing against you! But to Pilate's surprise, Jesus made no further reply.
Pilate, anxious to placate the crowd, released Barabbas for them and, after having Jesus scourged, he handed him over to be crucified. (Mark 15: 1-5, 15)
The Jewish court, with the high priest presiding, was called the Sanhedrin. And while the Sanhedrin was powerful, the Romans reserved the right to impose the death penalty on criminals. So for the court to have Jesus executed they had to have him judged by Pilate, the governor who represented the Roman Emperor in that far end of their empire.
The Jewish court condemned Jesus for his blasphemous claim to be one with God, but they knew that would be insufficient cause for his execution. So to be sure the Romans would carry out their bidding, they trumped up charges of treason, which the Romans would care about. The first thing any institution is interested in is preserving itself - so treason matters!
The whole affair was dirty: the Sanhedrin met at night (forbidden), Jesus had no defense witnesses, a death sentence was proclaimed even before the next day's trial before Pilate. For his part, Pilate, an unhappy man, unsuccessful in handling things in his district, caved in, assented to the execution and returned Jesus to the Jewish court, distancing himself from any responsibility.
Jesus knows it can be a sad and dirty world: cowardly, lazy, self-protective, dishonest. A teen-aged boy was pressed to the floor of the prison shower room by a gang of boy-men who raped him, beat him, stole his clothes and anything else he owned, threatening even worse damage if he talked. Those in the system, who should have protected him, (Pilate-like) looked the other way and denied having seen or heard anything out of the ordinary.