I know what they do. They look to the parents as the first suspects because they are the most likely "actors". Just like they look at the spouse as the most likely suspect when a husband or wife are murdered,or a business partner when a businessman is murdered. The police obviously looked at the VD's as suspects and dismissed them early-on. If they hadn't,John Walsh wouldn't have been there advising the family and arranging a PR firm to help them. He has contacts in the police dept that are at LEAST as good as those of a radio DJ,and I don't believe he would have stepped in and befriended them if they were still suspects in any way. Do you?
Pure speculation. :*)