I don't really know personally, but I found this....
https://www.justice.gov/archives/ag/advancing-justice-through-dna-technology-using-dna-solve-crimes
In cases where a suspect has not yet been identified, biological evidence from the crime scene can be analyzed and compared to offender profiles in DNA databases to help identify the perpetrator. Crime scene evidence can also be linked to other crime scenes through the use of DNA databases.
So my assumption is that since search warrants were issued for his home and stuff, that could be viewed as the "crime scene" since we really don't know what it is that they saw in there or found. The DNA from the jogging assault was in the system already and then it produced a hit? Even though he wasn't charged for that or named a POI, they have evidence a crime was committed within his home. I think for this case they are waiting for her/her body so they can charge him "fully" for what he did.
But then what I don't understand is...
today on the news they said Allen Park Police are going to send in the DNA from a sexual assault that happened there this month, to see if it is a match. Why wouldn't it already be there or would it have to be retested or something else? Maybe it was just the way they stated it on the news, since it doesn't say that in the article. But that didn't make sense to me, if the DNA taken from the jogger incident is what the connection was to Dani.
http://www.clickondetroit.com/news/...between-livonia-sexual-assault-case-their-own