Just finding that knife sheath with his DNA laying on the bed with the two dead girls is huge. Plus, there might be other DNA hits of his from the crime scene that we don't know about yet. The affidavit isn't going to go into more details about DNA, that's left for trial evidence IMO. All the cell phone tracking records and how it all correlates to this crime is also huge. And if they can find evidence that he purchased that kind of knife via computer forensics, etc then that's just more layers of evidence. Or maybe that knife was from his dad's house, maybe his dad's at one time - ?. With all that kind of evidence, it doesn't have to be proven that he was seen in the house, even though one roommate did see a person who fit his description. Just the DNA evidence itself, especially if any victim DNA is found in his car or apartment, is enough for a conviction. DNA is super hard to refute unless it's a sham trial like OJ's, which will not happen in this trial IMO.