The Sanhedrin and Pharisees deferred to Romans in ordering Jesus’ death 

In his weekly “Worship” column on March 31 (“Forgiveness should lead to conversion”) Father John Kiley posits that “Jews were not permitted capital punishment under Roman law.” That is why, he writes, “Jesus had to be hauled before Pilate.” I have heard this line of reasoning from other clerics.
Rome recognized Judaism as an ancient religion. Jews could impose a death sentence under Mosaic Law as in the case of the stoning of the first martyr, St. Stephen, which was witnessed by the Pharisee Saul according to the Acts of the Apostles.
The Sanhedrin and Pharisees were afraid of ordering the death of Jesus because of his popularity with a sizable number of Jews. That is why they passed the buck to the Romans. Only a Roman authority could impose death by crucifixion regarded as the most horrible form of punishment.
The procurator, Pontius Pilate, was a Roman pagan who believed in many gods. He could not have cared less that Jesus was talking about another deity and calling himself his son. Pilate heard the chant of the crowd hand-picked by the Pharisees to have Jesus crucified. Part of his job description was to keep the conquered lands peaceful. He had his hands full with those pesky Jewish zealots and did not want a riot on his watch
Pilate was also concerned that Jesus’ action in overturning their tables and driving out the money changers in the temple could impair the flow of tribute to Rome. He was reluctant to impose the death penalty and had Jesus flogged, a terrible punishment that could result in the death of the person on whom it was imposed. He relented when the crowd chose the zealot Barabbas and continued to chant for the crucifixion of Jesus.
Richard J. August, North Kingstown