Adding some old links:
http://www.nytimes.com/2005/01/10/national/10cape.html
http://www.wgbh.org/cainan/article?item_id=3097878
"We're trying to find that person who has something to hide," Sergeant Perry said.
Just because someone doesn't want their DNA collected, doesn't mean they have something to hide. What an underhanded way to get DNA samples.
This is no different that the police sweeps where they come around and ask permission to search your house for illegal guns. Anyone who doesn't have any, doesn't have anything to worry about and should let them in so they reason that anyone who doesn't let them in, must have illegal guns or they would have no reason to keep the police out.
And once they decline, then they become suspect not only of that crime, but of anything. So, they're damned if they do and damned if they don't.
I don't trust the government as far as I can spit.