Answer:
Hale quits the court at the end of Act 3 due to his frustrations.
Explanation:
He is frustrated because he finally acknowledges the irrationality and hysteria that have taken over the court proceedings. His conscience prevents him from further participating in these trials. He has changed since Act 1 because he no longer believes that Abigail and her posse are telling the truth and he sees that the judges are blind to the lies that they are telling. Hale also notices the court's corruption.
