HE HAD NOT YET SINNED
Actually, if you look a few verses ahead, Judas had already made the arrangements to betray Jesus.
Then one of the twelve, the one called Judas Is·car′i·ot, went to the chief priests and said: “What will YOU give me to betray him to YOU?” They stipulated to him thirty silver pieces. So from then on he kept seeking a good opportunity to betray him. - Mat 26:14-16
And Judas Is·car′i·ot, one of the twelve, went off to the chief priests in order to betray him to them. When they heard it, they rejoiced and promised to give him silver money. So he began seeking how to betray him conveniently. - Mark 14:10-11
Now the festival of the unfermented cakes, the so-called Passover, was getting near. Also, the chief priests and the scribes were seeking the effective way for them to get rid of him, for they were in fear of the people. But Satan entered into Judas, the one called Is·car′i·ot, who was numbered among the twelve; and he went off and talked with the chief priests and [temple] captains about the effective way to betray him to them. Well, they rejoiced and agreed to give him silver money. So he consented, and he began to seek a good opportunity to betray him to them without a crowd around. - Luke 22:1-6
In case you're trying to figure out how to work the Watchtower mistakes into conversation with a JW who comes to your door, the website is on the invitations. You can just say you went to the website after receiving one and had some questions. Since - being a Christian and in light of the season - you were reading the Bible about the last days of Christ on earth, you noticed some things didn't match what was online. This way you won't tip them off that you "know too much" and are an "opposer" or "apostate". Keep their wall down and keep them listening. Maybe, just maybe, they'll allow the Bible to speak to them without the taint of Watchtower spin.