That seems an especially good reason to distrust DNA evidence using the technique from this paper. It relies on such a small amount of DNA, in dust, that if someone opened a window and a stranger walked by, the interior of a room might be contaminated with the strangers DNA. Also people are mobile, their clothing will pick up DNA dust from one location and shed it in another location. There may already be DNA dust from a million people in any one location. Even if you suck the DNA directly out of the air, you don't know where that air has previously been.