New technology does much to empower us and to make life more convenient, but that same technology also empowers corporations and governments to watch us, to learn ever more about us and to use the information they collect in ways we cannot foresee and may not appreciate. The latest revelations about the scope and extent of the government’s programs of electronic surveillance remind us that our society faces some difficult challenges ahead as we strive to take the best advantage of new technology while protecting the dignity and privacy of individuals.

We can take some comfort in the Fourth Amendment’s ban on unreasonable searches and seizures and trust that the courts will protect us.

But we need to be wary, because the Fourth Amendment is only as powerful as the Supreme Court is willing to make it, and the court has recently demonstrated that its notion of a “reasonable” search seems to depend more on technological convenience than on concerns about individual liberty or personal privacy.

Just last week, the Supreme Court held, by a margin of 5-4, that the police may routinely take DNA samples from people who have been arrested for “serious crimes,” but who have not yet been tried or convicted.

Writing for the majority, Justice Anthony Kennedy characterized such DNA tests as a routine part of the booking procedure that police use when they process a suspect to be detained in custody.

Criminal suspects are regularly photographed and fingerprinted, and we now regard those as perfectly appropriate. Why not test suspects’ DNA, too?

The process of collecting the DNA sample is a little bit more invasive than having one’s fingers inked and pressed against a piece of paper, since it involves brushing a cotton swab against the inside lining of the cheek. But the operation takes only a moment and is perfectly harmless.

The majority concedes that taking a DNA sample constitutes a search under the Fourth Amendment, but that means only that the search needs to be “reasonable.” In their view, the search will be constitutional if the government’s reasons for wanting the information, on balance, outweigh the intrusiveness and indignity of the privacy violation.

Kennedy argues that the government has a weighty interest in establishing with certainty the identity of the persons the police have in custody. At one time, fingerprinting and photography provided the best means of identifying persons; now, the majority argues, DNA testing is the gold standard. If we don’t object to fingerprinting, how can DNA sampling and testing be any problem? On the other side, the cheek swabbing isn’t very intrusive, and no one who has been arrested can have all that much expectation of privacy anyway. Thus, he concluded, the search is constitutional.

The dissenting justices, Antonin Scalia, Ruth Bader Ginsberg, Sonia Sotomayor and Elena Kagan, object that the DNA testing is not really about identification at all. The police want DNA samples from the people they arrest, not to find out whether the people in custody are really who they say they are — fingerprinting already accomplishes that task of identification — but to find out whether they can link the people in custody to unsolved crimes.

The distinction matters because the Supreme Court has historically rejected such dragnet “suspicionless searches” as tools of law enforcement. And when it investigates crimes, the government is not supposed to search anyone unless it has a good reason why that person should be investigated.

If DNA testing is permitted when people are arrested for “serious crimes,” the dissenters ask, how soon will it be before DNA testing becomes routine for everyone pulled over on a traffic stop, or who seek to board an airplane, or who enter a government building?

In that event, a national DNA database could be built up that would facilitate crime-solving by making routine, suspicionless searches easy for the government to conduct. But it would also give public officials yet another way of keeping tabs on ordinary citizens.

Because all states permit the police to keep DNA records from people convicted of serious crimes, the only people really “searched” by the court-approved policy are those people who are arrested for and charged with serious crimes, but who are subsequently acquitted — i.e., those who are legally innocent and who most deserve the Fourth Amendment’s protection.

That is why the easier technology makes it for the government to trace, test and track us, the more zealously the court should guard our privacy, what Justice Louis Brandeis famously described as the “right to be let alone.”

Joseph R. Reisert is associate professor of American constitutional law and chairman of the department of government at Colby College in Waterville.