This does not just apply to the Rs- a dead body found in anyone's home places that person under suspicion, especially if they were also in the home at the time of death. So, it follows that if she were found in a neighbor's home (and that neighbor were at home at the time she died) that neighbor would then be a suspect. The fact that she was found in her own home is not meaningless. With very few exceptions, children reported "missing" or "kidnapped" that are later found dead in their own home are usually the victims of a relative, especially when found by a relative. LE takes these statistics very seriously, and that is the reason why the FBI (who have no particular interest in local Boulder politics LE) said "You'll be finding her body". And they did.
I didn't start out suspecting the parents. In fact, when I first heard of this horrible crime in December 1996, the first thought I had was that it was a jealous pageant mom. Then I thought it may have been someone who was a guest at the parents' party a few days before, maybe someone who even hid out in the house for a few days. But that didn't make sense- with the Rs planning a 2-week vacation right after Christmas, and getting home late Christmas Day, and possibly staying up even later, I just couldn't see someone who knew the family choosing that particular night to molest or kill her. By the same token, I can't see a stranger choosing that night, either, for the same reasons. Though a stranger wouldn't have known about the vacation plans, choosing a night when virtually all parents are home with their children doesn't make sense to ME. So as I began to look closer, I found that I couldn't see it happening any other way than by the hand of a family member.
I also looked with a suspicious eye at others- Wolf, Helgoth, etc. But there was nothing to link them to the crime, including the DNA. No fibers or hairs either.