I don't know what you saw but after Gail realized it was him who pushed her down the stairs David went round the street with a bar from the garage smashing windows and cars , he hurt ken and the police were called and he was arrested. People in the street were obviously angry with him but Gail stood by him, he came clean about everything he'd done to her and the family and stood up and took his punishment.

I think he wanted to get out of the mental state he was in so he didn't want to defend himself and took what was given. He made his apologies to the street and was sent down. I think seeing all the people around him has made him realize that he has not been badly done to and he has been a first class brat! He doesn't want to be in there but finally he has grown up! lets hope he stays that way!