[John Galt's cousin]

I see your point insofar as the DNA sample is used ONLY for purposes of identification. But what happens when every person arrested is tested and the database becomes huge?

Could the information become useful to the government for some other reason? (I am not sure what else they can find from DNA but am suspicious of people like Rham Emmanuel having access to any information about me.)

Used to match DNA evidence collected from a rape or violent felony victim - sure. Used to identify the person who licked a stamp on an envelope containing an anonymous complaint letter - I am not so sure.

[OldDeckHand]

"But what happens when every person arrested is tested and the database becomes huge?"

You mean like fingerprints, mugshots and photographs of gang tatoos are huge?

"Used to identify the person who licked a stamp on an envelope containing an anonymous complaint letter - I am not so sure."

You have no expectation of privacy of bodily fluids left on mail, or in other places that it's left in public. If you send a letter to the police, you have no expectation of privacy about the contents of that letter or about the physical letter itself.