If I were to guess, I believe that it's Westerfield. I also believe that he is the source of the "swinging" rumours, trying to cover his own ass by taking attention away from himself, and directing it at the van Dams.
Who else would have "leaked" that information to the press? A law enforcement officer? Why? Releasing information like that can only hurt the investigation. "Swinger" friends of the van Dams would not do it either, out of self-protection.
The discjockey has either been lied to, or is himself lying about his source.
That theory is not likely because the Van Dam's were questioned about it on national television. Now imagine, you are on national television to plead for the return of your daughter. Out of the blue comes questions asking if you are both swingers.
If you are NOT swingers, you just deny it and go on. If you ARE swingers, but do not wish to admit to it, but neither do you wish to lie....you deflect the question or chose not to answer the question.