It really depends what the law is in this universe. It's possible that DNA is automatically taken from all convicts, of any nature, or perhaps just potential or convicted felons. I would assume all felons (generally the crime entails more than a year in prison) would have their DNA in the system. Pheonix, for instance, is definitely in the system. Had his blood not been washed away by Ocean's antics, he definitely would've been linked to the site. The DNA of those arrested for having possibly committed felonies is also likely taken for evidence purposes.

So Collins and the police probably will have Ocean's and Finn's blood, but of course, without anyone to explicitly match it to in a database, it's pointless.