Pilate did not consider the charges convincing. So he told the Sanhedrin to judge Jesus by their own law. Pilate saw this as a Jewish argument, which he refused to investigate.
However, the Jewish leaders insisted that execution was necessary. This fulfilled the prediction Jesus made about how he would die (see 12:32–33). The Jews would have used stoning, but the Romans used crucifixion. If Pilate sentenced Jesus, the Romans would hang Jesus on a cross to die.