I will try and deal with several of the resulting questions without extensive explanations.

The reason that these requirements do not violate Constitutional provisions is that the right against self-incrimination is anchored in testimony, not un-spoken physical evidence. The only person in recent history to be required to testify against himself was Oliver North and several others in the Iran-Contra case and the Supreme Court dealt Congress a complete setback on that issue. Even Congress cannot compel a citizen to testify against his own self interest. However this does not apply to non-testimonial evidence, as I enumerated above. And once you think of it in that case, you can easily see why the DNA falls into that category. Suspects have had their fingerprints, and photos taken for years. Think of DNA as a biological photo.

Remember that there are five levels of legal culpability.

1. Articulatible Reason; the legal standard for conducting a traffic stop or to stop, question, and frisk a citizen.
2. Reasonable Suspicion; the standard for conducting a search of the person or property.
3. Probable Cause; the standard for an arrest.
4. Preponderance of Evidence; the standard for a finding in a Civil case.
5. Beyond a Reasonable Doubt; the standard for conviction in a Criminal case.

Each of those standards have volumes of legal discourse written about them, which I do not plan to replicate, but understand that those are the standards which a court looks at when deciding whether or not to admit evidence at a trial, and any evidence not meeting the appropriate standard is not admitted. As the laws are currently written, you would not be "an ordinary citizen" to have your DNA taken (with a cotton swab in the mouth to collect some cells from your gum line), but at least at level 2 above. And because of such issues as Chain of Custody (knowing who has handled the evidence) and specific prohibitions, the DNA is in no danger of becoming a genetic study database.

Now in some cases the police have asked local citizens to submit to a DNA test to try an find a serial rapist in a discrete community, but every citizen has the right at that level to refuse to take the test, (which under those situations, might put you into an investigative pool of one). But again that would be no real difference from taking your picture around to show to potential witnesses.

And even if you were not convicted of the crime charged, the law is clear that once it is legally collected under which ever standard applied at the time, the evidence can and will be retained for future use if need be.

I hope this clears matters up