Justice Kennedy writing for the majority in approving of this DNA collection scheme, consisting of himself, the Chief Justice, and Justices Thomas, Breyer, and Alito, emphasized how reasonable it was for police to have the best information available about who had been arrested:

The legitimate government interest served by the Maryland DNA Collection Act is one that is well established: the need for law enforcement officers in a safe and accurate way to process and identify the persons and possessions they must take into custody. ...When probable cause exists to remove an individual from the normal channels of society and hold him in legal custody, DNA identification plays a critical role in serving those interests. First, “[i]n every criminal case, it is known and must be known who has been arrested and who is being tried.” An individual’s identity is more than just his name or Social Security number, and the government’s interest in identification goes beyond ensuring that the proper name is typed on the indictment. Identity has never been considered limited to the name on the arrestee’s birth certificate. In fact, a name is of little value compared to the real interest in identification at stake when an individual is brought into custody. “It is a well recognized aspect of criminal conduct that the per-petrator will take unusual steps to conceal not only his conduct, but also his identity. Disguises used while committing a crime may be supplemented or replaced by changed names, and even changed physical features.” An “arrestee may be carrying a false ID or lie about his identity,” and “criminal history records . . . can be inaccurate or incomplete.” A suspect’s criminal history is a critical part of his identity that officers should know when processing him for detention. It is a common occurrence that “[p]eople detained for minor offenses can turn out to be the most devious and dangerous criminals. Hours after the Oklahoma City bombing, Timothy McVeigh was stopped by a state trooper who noticed he was driving without a license plate. Police stopped serial killer Joel Rifkin for the same reason. One of the terrorists involved in the September 11 attacks was stopped and ticketed for speeding just two days before hijacking Flight 93.” Police already seek this crucial identifying information. They use routine and accepted means as varied as comparing the suspect’s booking photograph to sketch artists’ depictions of persons of interest, showing his mugshot to potential witnesses, and of course making a computerized comparison of the arrestee’s fingerprints against electronic databases of known criminals and unsolved crimes. In this respect the only difference between DNA analysis and the accepted use of fingerprint databases is the unparalleled accuracy DNA provides.... [T]he use of DNA for identification is no different than matching an arrestee’s face to a wanted poster of a previously unidentified suspect; or matching tattoos to known gang symbols to reveal a criminal affiliation; or matching the arrestee’s fingerprints to those recovered from a crime scene.

In considering laws to require collecting DNA from arrestees, government agencies around the Nation found evidence of numerous cases in which felony arrestees would have been identified as violent through DNA identification matching them to previous crimes but who later committed additional crimes because such identification was not used to detain them. ... Present capabilities make it possible to complete a DNA identification that provides information essential to determining whether a detained suspect can be released pending trial. See, e.g., States Brief 18, n. 10 (“DNA identification database samples have been processed in as few as two days in California, although around 30 days has been average”). Regardless of when the initial bail decision is made, release is not appropriate until a further determination is made as to the person’s identity in the sense not only of what his birth certificate states but also what other records and data disclose to give that identity more meaning in the whole context of who the person really is. And even when release is permitted, the background identity of the suspect is necessary for determining what conditions must be met before release is allowed.

[I]n the interests of justice, the identification of an arrestee as the perpetrator of some heinous crime may have the salutary effect of freeing a person wrongfully imprisoned for the same offense. “[P]rompt [DNA] testing . . . would speed up apprehension of criminals before they commit additional crimes, and prevent the grotesque detention of . . . innocent people.” J. Dwyer, P. Neufeld, & B. Scheck, Actual Innocence 245 (2000).

The expectations of privacy of an individual taken into police custody “necessarily [are] of a diminished scope.” “[B]oth the person and the property in his immediate possession may be searched at the station house.” A search of the detainee’s person when he is booked into custody may “ ‘involve a relatively extensive exploration,’ ” including “requir[ing] at least some detainees to lift their genitals or cough in a squatting position." ....Here, by contrast to the approved standard procedures incident to any arrest detailed above, a buccal swab involves an even more brief and still minimal intrusion. A gentle rub along the inside of the cheek does not break the skin, and it “involves virtually no risk, trauma, or pain.”

Also, Kennedy argues, this helps in determining who should be released on bail:Also, BTW, your DNA can help some innocent dude go free, and isn't that great?And, hey: it's totally not intrusive, because once you've been arrested you really have no rights anyway:So, for those five, this is totally innocent, awesome, non-intrusive, and peachy-keen, and only affects Bad People anyway.

Justice Scalia, with whom Justice Ginsburg, Justice Sotomayor, and Justice Kagan join, dissented from this conclusion. And how:

The Fourth Amendment forbids searching a person for evidence of a crime when there is no basis for believing the person is guilty of the crime or is in possession of incriminating evidence. That prohibition is categorical and without exception; it lies at the very heart of the Fourth Amendment. Whenever this Court has allowed a suspicionless search, it has insisted upon a justifying motive apart from the investigation of crime. It is obvious that no such noninvestigative motive exists in this case. 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. And the Court’s comparison of Maryland’s DNA searches to other techniques, such as fingerprinting, can seem apt only to those who know no more than today’s opinion has chosen to tell them about how those DNA searches actually work.

At any rate, all this discussion is beside the point. No matter the degree of invasiveness, suspicionless searches are never allowed if their principal end is ordinary crime-solving. A search incident to arrest either serves other ends (such as officer safety, in a search for weapons) or is not suspicionless (as when there is reason to believe the arrestee possesses evidence relevant to the crime of arrest). Sensing (correctly) that it needs more, the Court elaborates at length the ways that the search here served the special purpose of “identifying” King. But that seems to me quite wrong—unless what one means by “identifying” someone is “searching for evidence that he has committed crimes unrelated to the crime of his arrest.” 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.” 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, and no court would hold such a search lawful. I will therefore assume that the Court means that the DNA search at issue here was useful to “identify” King in the normal sense of that word—in the sense that would identify the author of Introduction to the Principles of Morals and Legislation as Jeremy Bentham.

The portion of the Court’s opinion that explains the identification rationale is strangely silent on the actual workings of the DNA search at issue here. To know those facts is to be instantly disabused of the notion that what happened had anything to do with identifying King. King was arrested on April 10, 2009, on charges unrelated to the case before us. That same day, April 10, the police searched him and seized the DNA evidence at issue here. What happened next? Reading the Court’s opinion, particularly its insistence that the search was necessary to know “who [had] been arrested,” one might guess that King’s DNA was swiftly processed and his identity thereby confirmed—perhaps against some master database of known DNA profiles, as is done for fingerprints. After all, was not the suspicionless search here crucial to avoid “inordinate risks for facility staff” or to “existing detainee population"? Surely, then—surely—the State of Maryland got cracking on those grave risks immediately, by rushing to identify King with his DNA as soon as possible. Nothing could be further from the truth. Maryland officials did not even begin the process of testing King’s DNA that day. Or, actually, the next day. Or the day after that. And that was for a simple reason: Maryland law forbids them to do so. A “DNA sample collected from an individual charged with a crime . . . may not be tested or placed in the statewide DNA data base system prior to the first scheduled arraignment date.” Md. Pub. Saf. Code Ann. §2–504(d)(1)/ And King’s first appearance in court was not until three days after his arrest. (I suspect, though, that they did not wait three days to ask his name or take his fingerprints.)... The truth, known to Maryland and increasingly to the reader: this search had nothing to do with establishing King’s identity. It gets worse. King’s DNA sample was not received by the Maryland State Police’s Forensic Sciences Division until April 23, 2009—two weeks after his arrest. It sat in that office, ripening in a storage area, until the custodians got around to mailing it to a lab for testing on June 25, 2009—two months after it was received, and nearly three since King’s arrest. After it was mailed, the data from the lab tests were not available for several more weeks, until July 13, 2009, which is when the test results were entered into Maryland’s DNA database, together with information identifying the person from whom the sample was taken. Meanwhile, bail had been set, King had engaged in discovery, and he had requested a speedy trial—presumably not a trial of John Doe. It was not until August 4, 2009—four months after King’s arrest—that the forwarded sample transmitted (without identifying information) from the Maryland DNA database to the Federal Bureau of Investigation’s national database was matched with a sample taken from the scene of an unrelated crime years earlier.

The Governor of Maryland, in commenting on our decision to hear this case, said that he was glad, because “[a]llowing law enforcement to collect DNA samples . . . is absolutely critical to our efforts to continue driving down crime,” and “bolsters our efforts to resolve open investigations and bring them to a resolution.” Marbella, Supreme Court Will Review Md. DNA Law, Baltimore Sun, Nov. 10, 2012, pp. 1, 14. The attorney general of Maryland remarked that he “look[ed] forward to the opportunity to defend this important crime-fighting tool,” and praised the DNA database for helping to “bring to justice violent perpetrators.” ...The Maryland regulations implementing the Act confirm what is now monotonously obvious: These DNA searches have nothing to do with identification.

The Court does not actually say whether it believes that taking a person’s fingerprints is a Fourth Amendment search, and our cases provide no ready answer to that question. Even assuming so, however, law enforcement’s post-arrest use of fingerprints could not be more different from its post-arrest use of DNA. Fingerprints of arrestees are taken primarily to identify them (though that process sometimes solves crimes); the DNA of arrestees is taken to solve crimes (and nothing else).... The Court asserts that the taking of fingerprints was “constitutional for generations prior to the introduction” of the FBI’s rapid computer-matching system. This bold statement is bereft of citation to authority because there is none for it. The “great expansion in fingerprinting came before the modern era of Fourth Amendment jurisprudence,” and so we were never asked to decide the legitimacy of the practice. As fingerprint databases expanded from convicted criminals, to arrestees, to civil servants, to immigrants, to everyone with a driver’s license, Americans simply “became accustomed to having our fingerprints on file in some government database.” But it is wrong to suggest that this was uncontroversial at the time, or that this Court blessed universal fingerprinting for “generations” before it was possible to use it effectively for identification. The Court also assures us that “the delay in processing DNA from arrestees is being reduced to a substantial degree by rapid technical advances.” The idea, presumably, is that the snail’s pace in this case is atypical, so that DNA is now readily usable for identification. The Court’s proof, however, is nothing but a pair of press releases—each of which turns out to undercut this argument. We learn in them that reductions in backlog have enabled Ohio and Louisiana crime labs to analyze a submitted DNA sample in twenty days. But that is still longer than the eighteen days that Maryland needed to analyze King’s sample, once it worked its way through the State’s labyrinthine bureaucracy. What this illustrates is that these times do not take into account the many other sources of delay. So if the Court means to suggest that Maryland is unusual, that may be right—it may qualify in this context as a paragon of efficiency. (Indeed, the Governor of Maryland was hailing the elimination of that State’s backlog more than five years ago. See Wheeler, O’Malley Wants to Expand DNA Testing, Baltimore Sun, Jan. 11, 2008, p. 5B.) Meanwhile, the Court’s holding will result in the dumping of a large number of arrestee samples—many from minor offenders—onto an already overburdened system: Nearly one-third of Americans will be arrested for some offense by age 23. See Brame, Turner, Paternoster, & Bushway, Cumulative Prevalence of Arrest From Ages 8 to 23 in a National Sample, 129 Pediatrics 21 (2011).

What DNA adds—what makes it a valuable weapon in the law-enforcement arsenal—is the ability to solve unsolved crimes, by matching old crime-scene evidence against the profiles of people whose identities are already known. That is what was going on when King’s DNA was taken, and we should not disguise the fact. Solving unsolved crimes is a noble objective, but it occupies a lower place in the American pantheon of noble objectives than the protection of our people from suspicionless law-enforcement searches. The Fourth Amendment must prevail.

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].” 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. The most regrettable aspect of the suspicionless search that occurred here is that it proved to be quite unnecessary. All parties concede that it would have been entirely permissible, as far as the Fourth Amendment is concerned, for Maryland to take a sample of King’s DNA as a consequence of his conviction for second-degree assault. So the ironic result of the Court’s error is this: The only arrestees to whom the outcome here will ever make a difference are those who have been acquitted of the crime of arrest (so that their DNA could not have been taken upon conviction). In other words, this Act manages to burden uniquely the sole group for whom the Fourth Amendment’s protections ought to be most jealously guarded: people who are innocent of the State’s accusations. Today’s judgment will, to be sure, have the beneficial effect of solving more crimes; then again, so would the taking of DNA samples from anyone who flies on an airplane (surely the Transportation Security Administration needs to know the “identity” of the flying public), applies for a driver’s license, or attends a public school. Perhaps the construction of such a genetic panopticon is wise. But I doubt that the proud men who wrote the charter of our liberties would have been so eager to open their mouths for royal inspection. I therefore dissent, and hope that today’s incursion upon the Fourth Amendment, like an earlier one, will some day be repudiated.

He's just getting started:Justice Scalia proceeds to call bullshit on more of the majority's reasoning:You know who else knows the "we're just doing this to identify people" argument is bullshit? Gov. Martin O'Malley, says Justice Scalia:Also, Justice Scalia explains, this ain't fingerprinting, and it ain't fast:Which leads us to the Big Finish, and it's a big one:Is it just me, or is Minority Report feeling more like a documentary every day?