LE has repeatedly said theyve obtained what is likely the killers DNA at the crime scene. Had they matched it to a POI, that person no doubt would be arrested (unless that person has an innocent explanation for their DNA being left at the crime scene). The possibility exists (presumably) that the unidentified DNA at the crime scene belongs to someone with no connection to the murders; one of the victims, for example, might have picked it up by accident somewhere. But, based on their statements, LE seems to be pretty sure it belongs to the killer. Nobody has been ruled out through DNA, therefore, because, even though there is no match, the DNA could still belong to someone other than the killer. So, LE has to leave themselves some wiggle room. Still, not being ruled in through DNA is significant, even if it cannot be definitive.
From:
http://www.jconline.com/story/news/...swers-soon-delphi-double-homicides/713451001/
He said police also have obtained samples of Nations' DNA, which has become a common procedure over the course of the seven-month-long investigation. He added that the samples will be compared to evidence gathered at the crime scene. "We check DNA on everybody that has been investigated," Riley said. "Every person that we have talked to, we've gotten a DNA swab from."
