At the last Paschal supper the Savior spoke aloud to all the apostles, not excluding Judas, who was present with them: "The Son of Man goes as it is written of Him, but woe to that man by whom the Son of Man is betrayed. It would have been good for that man if he had not been born."
Then Judas, who betrayed Him, said, "Is it I, Rabbi?" Jesus said to him, "You have said so" (Mt 26:24).
Therefore, if Judas could disregard so powerful a warning, his sin was an act of free will. The abuse of freedom does not cease to be sin because it was foreseen by the Lord's omniscience.
If Judas's betrayal was turned by the all-good providence into an instrument for attaining the saving goal, then glory and thanksgiving belong to the wisdom and goodness of God, who directs evil toward good.
Yet the act of an evil will remains what it is. In the person of Judas it is all the more worthy of condemnation because, even after committing the crime, he could have been saved if he had not fallen into despair.
Despair destroyed him. If, having recognized the gravity of his sin, he had turned to the Lord with hope in God's mercy, begged forgiveness, and promised to devote the rest of his life to works of repentance, there is no doubt he would have been pardoned.
Perhaps he might even have proved useful to the Church of Christ, like Paul. Paul had been a cruel persecutor of Christians, but, after repenting, he became a chosen vessel of God's grace and labored more than all the Apostles in preaching the Gospel.
Thus, although Christ knew that the one He had chosen as an Apostle would betray Him and perish, Christ was not the author of his crime or perdition.