What does Luke 22:71 mean?
The Sanhedrin gets the testimony it needs. This is Jesus' third trial. In the second, some of the same people asked Him the same question: "Tell us if you are the Christ, the Son of God." Jesus answered in the same way: "You have said so," a vague assent. At that point, the high priest tore his robes and the other religious leaders present agreed Jesus deserved death (Matthew 26:63–66).Luke records little of that trial (Luke 22:63–65). This is the official trial before the whole Sanhedrin. Whatever Jesus said in the previous two trials doesn't matter legally. They need to get Him to repeat His words.
He does so. First, He claims to be the Son of Man who will sit at God's right hand (Luke 22:69). The council considers such familiarity with God to be blasphemy. Now, He does not deny that He is the Son of God. Not only is blasphemy according to their point of view, but it is an insult to the Romans: for them, only the emperor is the son of God.
Jesus' enemies have what they need. They can now take Jesus to Pilate and demand that Jesus deserves death. They frame Jesus' crime as claiming to be the king of the Jews, a rival to the emperor. Pilate sends Jesus to Herod Antipas, who can't get Jesus to say anything. Pilate knows Jesus isn't a threat to the emperor. But he also knows that the Sanhedrin could ruin him if they make good on their threat to send word that Pilate has shown mercy to someone guilty of sedition (John 19:12). So, Pilate gives them what they want and sends Jesus to the cross (Luke 23).