I don't understand why. My guess would be that even the best of people sometimes forget things that are important like the truth. David was ashamed of what they had done and his part in it. Although he never did get the official okay that Mr. Griffin was his father, I believe that he deduced the truth and was very heartbroken in the end. In my ownself, I believe that I would change if I killed a man, even more if it was somebody that I know, and if it just happened to be my longlost father, well . . . I would not be the same. david changed from this experience, and it is quite possible that it wasn't for the better.

Ummm. I think it's kind of obvious. And I havent even gotten to chapter four. I believe it's to avoid getting caught, no?