Murder is the unlawful killing of another human. The crucifixion was not against the law. Don't want to recognize the law? Fine, but as long as it's not against the law of the land you have no case for murder..
It seems to me from reading the accounts that the Jews had no case against Jesus for blasphemy because he never claimed to be God.
Jesus in his defense before the Jews said...."I displayed to you many fine works from the Father. For which of those works are you stoning me?” 33 The Jews answered him: “We are stoning you, not for a fine work, but for blasphemy; for you, although being a man, make yourself a god.” 34 Jesus answered them: “Is it not written in your Law, ‘I said: “You are gods”’? 35 If he called ‘gods’ those against whom the word of God came—and yet the scripture cannot be nullified— 36 do you say to me whom the Father sanctified and sent into the world, ‘You blaspheme,’ because I said, ‘I am God’s Son’?" (John 10:32-36)
He only ever said he was God's son. After his arrest, and Pilate's attempt o free him, the Jews showed how desperate they were to be rid of this man......
Matthew 27:24-26...."Seeing that it did no good but, rather, an uproar was arising, Pilate took water and washed his hands before the crowd, saying: “I am innocent of the blood of this man. You yourselves must see to it.” 25 At that all the people said in answer: “Let his blood come upon us and upon our children.” 26 Then he released Bar·abʹbas to them, but he had Jesus whipped and handed him over to be executed..."
They cursed themselves and their children with his blood. I believe they got their wish.
Luke 23:22-25..."The third time he said to them: “Why? What bad thing did this man do? I found in him nothing deserving of death; I will therefore punish him and release him.” 23 At this they became insistent, demanding with loud voices that he be executed, and their voices prevailed. 24 So Pilate made the decision that their demand be met. 25 He released the man whom they were demanding, who had been thrown into prison for sedition and murder, but he surrendered Jesus to their will."
John 19:12; 15...."For this reason Pilate kept trying to find a way to release him, but the Jews shouted: “If you release this man, you are not a friend of Caesar. Everyone who makes himself a king speaks against Caesar.” ....Pilate said to them: “Shall I execute your king?” The chief priests answered: “We have no king but Caesar.” 16 Then he handed him over to them to be executed..."
The Roman governor found no case against Jesus under Roman Law so he wanted to release Jesus. The Jews threatened to report him for sedition if he didn't agree to the execution. (speaking against Caesar carried the death penalty) So he publicly washed his hands of the whole affair, had Jesus flogged just to appease them, and handed him over for execution.
The Jews had held an illegal trial (on the night of the Passover) and had furnished false witnesses in order to carry out their plans. Thus, when Jesus said "forgive them Father for they know not what they do" he was NOT talking about the Jewish leaders.....they conspired together to make sure that Jesus was going to die. So he was referring to the Roman soldiers who drove the nails and hoisted him up to die an agonizing death on that torture stake when he asked God to forgive them. Only after Jesus died and the earthquake that resulted at that moment, did the soldiers realize what they had done.