Sorry if this is a dumb query, but did the McCanns have dogs? Like others have posted recently, pet hairs have a way of getting absolutely everywhere. Likewise could previous guests have transferred dog hairs? Just for the purpose of ruling out any innocent reason for dog hairs in the apartment.
I always check under the bed in hotels before checking out, and it is often apparent that the room hasn't been thoroughly cleaned.
Anyway I suppose the only relevance here would be if those dog hairs were identified as CB's dogs' hairs.
Some interesting previous investigations into dog hairs at murder scenes. In one case a murdurer had dog hairs in his house which matched the dog of his victim, and were likely transferred from her pyjamas.
Also, an interesting difference between human and dog/cat hair DNA analysis: “The unique thing about animal hair is that dogs and cats groom themselves, so they are putting saliva on the shaft of the hair. We are more likely to find DNA [on animal hair] than on human hair because animal saliva is individual. Then animal DNA can be used as one of the pieces of the evidence puzzle.”
BBC News - Detectives solved murder case using dog DNA
Forensic Cases: The Murder of Leanne Tiernan
How Animal DNA Puts Killers Behind Bars
