The context the DNA was found in, on the waistband and in the underwear, were areas selected by the police because they were considered relevant to the crime that happened.
You mean selected by the DA's office. And that's EXACTLY the problem! They picked areas that THEY considered relevant because they had already DECIDED what happened. That's okay, as long as IDI does it, apparently!
They had a POSITIVE result while testing criminally relevant surfaces.
I don't suppose you'd know just off the top of your head any of the OTHER places they tested, or IF they tested any other places, just to make sure they weren't off on a(nother) wild goose chase?