from opinions rendered in Maryland v. King

Justice Kennedy penned the majority opinion in Maryland v. King, which ruled "... that DNA identification of arrestees is a reasonable search that can be considered part of a routine booking procedure ..." This means the cops can swab the inside of the cheek of someone who gets arrested, so long as that someone is being detained for a "serious offense". In giving the majority opinion, Kennedy goes on at length praising the role of DNA in identifying people. He points out that, had Timothy McVeigh been swabbed when he was stopped for not having a license plate hours after he bombed the federal building in Oklahoma City, then the cop could have known it was McVeigh. Or, had one of the 9-11 hijackers been swabbed when he was ticketed for speeding days before the atrocity, the cop would have identified him, too. Of course, nevermind that these identifications would not have prevented anything, and that neither terrorist was being arrested at the time. Kennedy's reasonings are impressively dense. And Justice Scalia calls him out for it.

In the dissent, Scalia writes, "The Court’s assertion that DNA is being taken, not to solve crimes, but to identify those in the State’s custody, taxes the credulity of the credulous." Then he goes on:

... while the Court is correct to note (ante, at 8–9) that there are instances in which we have permitted searches without individualized suspicion, “[i]n none of these cases. . . did we indicate approval of a [search] whose primary purpose was to detect evidence of ordinary criminal wrongdoing.” Indianapolis v. Edmond, 531 U. S. 32, 38 (2000).

Just how intrusive is the cotton swab? Maybe that's beside the point, as Scalia notes:

And could the police engage, without any suspicion of wrongdoing, in a “brief and . . . minimal” intrusion into the home of an arrestee—perhaps just peeking around the curtilage abit? See ante, at 26. Obviously not.

And what of the purpose of identifying people? Is identifying someone really so innocent? No, Scalia argues:

At points the Court does appear to use “identifying” in that peculiar sense—claiming, for example, that knowing “an arrestee’s past conduct is essential to an assessment of the danger he poses.” Ante, at 15. If identifying someone means finding out what unsolved crimes he has committed, then identification is indistinguishable from the ordinary law enforcement aims that have never been thought to justify a suspicionless search. Searching every lawfully stopped car, for example, might turn up information about unsolved crimes the driver had committed, but no one would say that such a search was aimed at “identifying” him ...

But what if the State really is just identifying people without intending to solve crimes for which no probable cause to search exists?

The truth, known to Maryland and increasingly to the reader: this search had nothing to do with establishing King’s identity.
...
DNA testing does not even begin until after arraignment and bail decisions are already made. The samples sit in storage for months, and take weeks to test. When they are tested, they are checked against the Unsolved Crimes Collection—rather than the Convict and Arrestee Collection, which could be used to identify them.The Act forbids the Court’s purpose (identification), but prescribes as its purpose what our suspicionless-search cases forbid (“official investigation into a crime”). Against all of that, it is safe to say that if the Court’s identification theory is not wrong, there is no such thing as error.

So, all that said, what does the majority's errant ruling promise for the future?

The Court disguises the vast (and scary) scope of its holding by promising a limitation it cannot deliver. The Court repeatedly says that DNA testing, and entry into a national DNA registry, will not befall thee and me, dear reader, but only those arrested for “serious offense[s].” Ante, at 28; see also ante, at 1, 9, 14, 17, 22, 23, 24 (repeatedly limiting the analysis to “serious offenses”). I cannot imagine what principle could possibly justify this limitation, and the Court does not attempt to suggest any. If one believes that DNA will “identify” someone arrested for assault, he must believe that it will “identify” someone arrested for a traffic offense. This Court does not base its judgments on senseless distinctions. At the end of the day, logic will out. When there comes before us the taking of DNA from an arrestee for a traffic violation, the Court will predictably (and quite rightly) say, “We can find no significant difference between this case and King.” Make no mistake about it: As an entirely predictable consequence of today’s decision, your DNA can be taken and entered into a national DNA database if you are ever arrested, rightly or wrongly, and for whatever reason.