Deciding its biggest genetic privacy case of the term, a fractured Supreme Court said today that the states may take DNA samples from anybody arrested for serious crimes.

Privacy groups and law enforcement officials were closely watching the case because at least 27 states and the federal government have regulations requiring suspects to give a DNA sample upon some type of arrest, regardless of conviction. In all the states with such laws, the DNA records are cataloged in state and federal crime-fighting databases.

In a 5-4 decision, (.pdf) the justices reversed a 2012 ruling from Maryland's top court, which had said that it was a breach of the Fourth Amendment right against unreasonable search and seizure to take, without warrants, DNA samples from suspects who have been arrested for crimes ranging from attempted burglary to murder. In the end, Justice Anthony Kennedy wrote that swabbing the inside of a suspect's cheek to acquire a DNA sample was "an advanced technique superior" to fingerprinting, mugshots and even tattoo matching.

A DNA profile is useful to the police because it gives them a form of identification to search the records already in their valid possession. In this respect the 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. DNA is another metric of identifica­tion used to connect the arrestee with his or her public persona, as reflected in records of his or her actions that are available to the police.

Kennedy added that, not "to insist on fingerprints as the norm would make little sense to either the forensic expert or the layperson." The majority also said that DNA collection "may have the salutary effect of freeing a person wrongfully imprisoned for the same offense."

Justice Antonin Scalia, writing in dissent, said taking the DNA without a warrant was a clear Fourth Amendment violation. He suggested that the United States' founding fathers would not be so willing "to open their mouths for royal inspection."

DNA testing in the United States was first used to convict a suspected Florida rapist in 1987, and has been a routine tool to solve old or so-called cold cases. It has also exonerated convicts, even those on death row.

At issue before the justices was a Maryland Court of Appeals ruling that arrestees have a "weighty and reasonable expectation of privacy against warrantless, suspicionless searches" and that expectation was not outweighed by the state's "purported interest in assuring proper identification" of a suspect.

The case involved Alonzo King, who was arrested in 2009 on assault charges. A DNA sample he provided linked him to an unsolved 2003 rape case, and he was later convicted of the sex crime. But the Maryland Court of Appeals reversed, saying his Fourth Amendment rights were breached.

Maryland prosecutors had argued that mouth swabs were no more intrusive than fingerprinting. Maryland's high court said that it "could not turn a blind eye" to what it called a "vast genetic treasure map" that exists in the DNA samples retained by the state.

The Maryland court was noting that DNA sampling is much different from compulsory fingerprinting. A fingerprint, for example, reveals nothing more than a person's identity. But much more can be learned from a DNA sample, which codes a person's family ties, some health risks and, according to some, can predict a propensity for violence.

In dissent, Justice Antonin Scalia wrote that the cheek swabbing was an unconstitutional, warrantless search of a suspect because it goes beyond identifying the suspect and moves into crime-solving territory.

"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," Scalia wrote.

Scalia also mocked the majority's rationale because the suspect's DNA in the case was not processed for about four months after his arrest.

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.

The issue before the justices did not contest the long-held practice of taking DNA samples from convicts. The courts have already upheld DNA sampling of convicted felons, based on the theory that those who are convicted of crimes have fewer privacy rights.

Today's outcome was of no surprise, however. Chief Justice John Roberts in July stayed the Maryland decision. In the process, he said there was a "fair prospect" (.pdf) the Supreme Court would reverse the decision.