The day that DNA cheek swabs officially became the new fingerprints deserves to be marked and remembered -- and not just because of the inevitable march of technology.

No, the Supreme Court’s 5-4 holding today in Maryland v. King, that anyone arrested for a “serious crime” can have his or her DNA taken without any suspicion, is a landmark because it represents a major step toward a “Gattaca” world. This means that evidence of a crime can be collected without any particular suspicion, avoiding the pesky requirement of a warrant that the Founding Fathers thought would give us liberty and privacy.

Justice Anthony Kennedy’s majority opinion treats the standard collection of DNA samples from arrestees in Maryland as the logical outgrowth of the state’s interest in identifying the people it has arrested. This is a bit of a surprise from Kennedy, who can generally be counted on to embrace liberty. Yet in this case, he wrote, the state’s interest in keeping track of everyone it has arrested can be satisfied more accurately by DNA than by fingerprinting. And the swab of the cheek is, he said, little more invasive than a fingerprint.

If DNA sampling was actually like fingerprinting, this argument might be convincing. But of course it isn’t. Fingerprints are a phenotype that reveals nothing except a random pattern that no two individuals share. DNA, however, is your genotype: the blueprint for your entire physical person. If the government has my fingerprints, it’s like they have my randomly assigned Social Security number. If it has my DNA, it’s like they have the entire operating system.

Full Blueprint

That DNA is a full blueprint matters in two major ways: The first and most basic is that when the state possesses genetic information, it can -- and in the future, almost certainly will -- know vast amounts about the person whose genes are typed. The court said this wasn’t a worry because Maryland law prohibits the use of DNA information beyond identification. But in a world where every arrestee is sampled, how long will that legal principle last?

Yet it was the second concern that exercised Justice Antonin Scalia in his pungent dissent. Ordinarily, Scalia explained, a search can be performed only on probable cause and with a warrant. Fingerprints are not a search. But DNA is a search, and for a very important reason: The DNA of the petitioner, Alonzo Jay King Jr., was used to link him to the rape he was accused of committing. In other words, said Scalia, the purpose of the search and the swab wasn’t to identify the accused with a unique marker. It was to solve a crime in question.

If Scalia’s distinction seems subtle, it shouldn’t. Fingerprints are generally used for bureaucratic identification and only occasionally to solve a crime -- when the criminal has been careless enough to leave them behind. DNA, by contrast, hasn’t, thus far, been used for bureaucratic identification. It is useful primarily for solving crimes, since it is almost impossible not to leave some DNA behind wherever we may go and whatever we may do. To prove the point, Scalia demonstrated that King’s DNA sat around for weeks before being analyzed -- and was eventually analyzed to solve a crime, not to keep track of the criminal.

What is remarkable, then, is that even Justice Scalia -- joined by the liberals Ruth Bader Ginsburg, Elena Kagan and Sonia Sotomayor -- thinks there would be nothing wrong with sampling every arrestee’s DNA if the purpose really were just to keep tabs on them. The constitutional objection focuses on what the DNA is actually used for. However, these two functions -- bureaucratic identification and crime solving -- can probably never be fully separated in the real world. As technology improves, the DNA database could be employed to solve crimes even if its primary purpose were just to be for bureaucratic classification. The reason, again, is the nature of DNA itself, which is not only unique but also oozes from our every pore.

Libertarian Impulse

Justice Scalia’s libertarian impulse forms a real contrast with his conservative colleagues. It can be seen in his greater precision of language: Only Scalia, among the court’s conservatives, would build an opinion on the distinction of two different meanings of the word “identification.” Furthermore, Scalia distrusts the administrative state’s tendency to subsume the criminal-justice system. The fear that bureaucracy swallows rights -- and that our criminal-justice liberties are vulnerable to this process -- has also been reflected in Scalia’s repeated votes to strike down the federal sentencing guidelines.

On the other side, Justice Stephen Breyer’s decisive vote with the conservatives to provide a majority today is also characteristic and worth noting. Breyer is a pragmatic rationalist whose sympathies usually lie with effective bureaucratic administration. From his standpoint, it would be naive and silly to stand in the way of inevitable technological progress.

This case, then, posed a choice between technological state power and Luddite liberty. Liberty lost. Remember the day.

(Noah Feldman, a law professor at Harvard University and the author of the forthcoming “Cool War: The Future of Global Competition,” is a Bloomberg View columnist. Follow him on Twitter.)

To contact the writer of this article: Noah Feldman at noah_feldman@harvard.edu

To contact the editor responsible for this article: Tobin Harshaw at tharshaw@bloomberg.net