It seems like there is a general belief that RAT's DNA must have previously been obtained, identified, tested and the result entered into the Virginia and national databases. But, if it was only officially requested and obtained after Alexis' disappearance, his name may have only been on a list of many possible contributors/relatives whose unknown DNA matched a known sample.
But, unless LE had evidence or suspicion of a crime, they can't just go arrest someone or demand a clean DNA sample. Just because that person's name comes up as a possible contributor of the unknown sample...simply because they popped up as a relative through familial DNA. LE can't just arrest that person.
LE had to have probable cause to obtain DNA on RAT. The video from the Liberty, showing RAT near Alexis, may have provided the probable cause to request a search warrant and then to arrest RAT. Once arrested, under a violent felony charge, the commonwealth was able to collect a direct sample from RAT which, IMO, is the exact match to the one previously labeled unknown.
If LE got a familial hit before obtaining, securing, transporting, testing and entering RAT's and before he was arrested on the 11th. That may have been the reason, they swooped down on him so quickly.
The way it works is the unknown sample is entered into the database. When run against every other submitted sample, there may be a familial hit or hits. If there is a link, LE must then track down the known contributor and rely on basic investigative skills and on that person telling LE who their relatives are and how to find them.
It is not a simple process. It also true that even if RAT did have occasion to submit a DNA sample, that sample may not have been entered into a database until there was an actual conviction. If there was no conviction because the charges were dismissed or nollie'd, then RAT could have formally requested his sample and data be expunged.
So, until we know when this Familial Match occurred and when the potential suspect was questioned, arrested and gave his DNA sample, I will leave open that the possibility that RAT was on a list of possible suspects and LE just needed probable cause to arrest him.
