I think that's coming from AT (the Defense) and we have no reason to disbelieve her. She was pretty much crowing about the fact that there's "no known" connection between BK, his apartment or car, and the victims (which I take to mean "no victim DNA or hair in any of those places.") A lot of people on the internet felt that unless there was victim blood/DNA somewhere in his car or home, that the DNA at the scene wasn't enough (!)
So, I was very very disappointed, but had prepared myself all along for it, because I believe the killer's main goal was to avoid a lot of blood on himself and that he took steps ("The Perfect Crime Planner" playbook) to keep victim blood out of his car.
If there is such evidence, than AT has denied its existence publicly. I guess it remains to be seen, at trial.
IMO.