. Why does John Grady end up in court telling the story of the horse to the judge?

John Grady to take his riderless horses alone to the border. Days later, after braving snow, storms, icy wind, he rides into Langtry, Texas. For weeks, he rides through the border country seeking the owner of Blevins' horse. When multiple claims are made, the county constable impounds the horse and John Grady is ordered to appear in court. He tells the judge of his ordeal, answers his questions dutifully, and shows him the bullet wound in his leg. The judge awards John Grady custody of the horse. Later that night John Grady goes to the home of the judge and as if driven to purge his soul, tells him that he killed a man in jail and nearly killed another (the captain).