When the knight is convicted of his crime what does queen Guinevere decide

she decapitates him

Explanation:

Overcome by lust and his sense of his own power, he rapes her. The court is scandalized by the crime and decrees that the knight should be put to death by decapitation. However, Arthur's queen and other ladies of the court intercede on his behalf and ask the king to give him one chance to save his own life.