Linda Greenhouse on the Supreme Court and the law.

Police officers following a suspect into an apartment complex in Lexington, Ky., don’t know which apartment their man has entered. But wafting through one of the closed apartment doors is the familiar odor of marijuana. The smell provides reason to believe criminal activity is afoot, probable cause for a warrant to search the apartment.

Do the police stake out the apartment and go for a warrant? No, they do not. Instead, they bang on the door, shouting, “Police, police, police.” No response — at least, no verbal response. From behind the door the officers hear the sound of “people inside moving” and objects “being moved.” Aha! Evidence may be about to be destroyed. Announcing that they are coming in, the officers kick in the door and find not the man they were looking for, but three other people, one of whom is smoking marijuana. More marijuana, along with cocaine, is in plain view.

I don’t know about other people, but I have never found an uninvited encounter with the police to be a source of comfort.

The Fourth Amendment, of course, generally prohibits searches, especially searches of the home, that have not been authorized by a warrant. But like everything else, there are exceptions. The question for the Supreme Court in a case decided on Monday was whether the police behavior in this case, Kentucky v. King, came within a recognized exception to the warrant requirement, the “exigent circumstance” created by the likely imminent destruction of criminal evidence.

The Supreme Court of Kentucky, hardly the most radical of courts in hardly the blue-est of states, applied its understanding of the Fourth Amendment and said no. If instead of pounding on the door, the state court noted, the police had quietly gone to a magistrate and obtained a search warrant, the people in the apartment would have had no reason to start scurrying around destroying their valuable contraband. Because the police themselves had prompted that response, foreseeably creating the “exigent circumstance,” the court concluded that the state should not be allowed to reap the benefit.

The United States Supreme Court reversed. The vote was 8 to 1. Hello? Is anyone home? (And I don’t mean Justice Ruth Bader Ginsburg, the lone dissenter.)

Fourth Amendment law is enormously complex (although not as complex as it once was, now that the state wins almost all the cases) and I make no pretense here of unpacking it wholesale. Nor do I argue that this case was the most important on the court’s docket; even accepting Justice Ginsburg’s conclusion that the police could easily have obtained a warrant and that the majority had gratuitously used the case “to contract the Fourth Amendment’s dominion,” the criminal justice system has hardly been shaken to its core.

But in fact, its very ordinariness is what makes this decision worth pondering. It’s worth stopping to consider the assumptions about human nature that underlie not only this ruling but much of the court’s Fourth Amendment jurisprudence. It’s worth wondering what planet the justices — most of them, anyway, and not just the incumbents, but many of their predecessors — have been living on when it comes to encounters between the police and the rest of us.

What the court held, in an opinion by Justice Samuel A. Alito Jr., is that warrantless entry to prevent the destruction of evidence is justified as long as the police “did not create the exigency by engaging or threatening to engage in conduct that violates the Fourth Amendment.”

Here, according to the court, all the police did was knock on the door, something that is “no more than any private citizen might do.” (But didn’t the police break the door down and barge in — hardly something one would expect to follow a neighborly knock? Well, yes, but that was after the “exigency” arose, after they heard the scurrying.)

According to Justice Alito, “Whether the person who knocks on the door and requests the opportunity to speak is a police officer or a private citizen, the occupant has no obligation to open the door or to speak.” In other words, the occupants of the apartment not only had a right to tell the police to go away, they almost had a constitutional obligation to do so, because “occupants who choose not to stand on their constitutional rights but instead elect to attempt to destroy evidence have only themselves to blame for the warrantless exigent-circumstances search that may ensue.”

“Only themselves to blame.” But wait, there’s more. It turns out that the occupants of this apartment were not only woefully unsophisticated about the Fourth Amendment, they were also ingrates: “Citizens who are startled by an unexpected knock on the door or by the sight of unknown persons in plain clothes on their doorstep may be relieved to learn that these persons are police officers. Others may appreciate the opportunity to make an informed decision about whether to answer the door to the police.”

An opportunity to ask the officers to “hold it right there while I consult my attorney?” Let’s get real.

I don’t know about other people, but I have never found an uninvited encounter with the police to be a source of comfort. Once, driving through a quiet residential neighborhood in Washington on the way home from a theater performance, my husband and I were unaccountably pulled over by a police officer in a squad car. The officer asked my husband (a lawyer) for his license and registration. Did he comply? Of course. It occurred to neither of us to say: “Officer, I invoke the Fourth Amendment and request that you articulate the suspicion that has caused you to pull us over.” We had not been drinking or using drugs, we had nothing to hide, and we had broken no law. But the incident was nonetheless unnerving, and my blood pressure goes up as I recall it years later.

The Supreme Court’s fantasy world of consensual and constitutionally informed encounters with the police is nothing new. In a 1984 decision, Immigration and Naturalization Service v. Delgado, a case arguably even more relevant today than it was before the immigration crackdown of the later 1980’s and since, the court rejected a Fourth Amendment challenge to immigration sweeps of factories and other workplaces. There was no problem, the court held, because the workers surrounded by immigration agents were not “seized.” They were free to leave the premises, and those who chose to remain participated in nothing more than a “classic consensual encounter.”

In 1991, the court upheld a police technique known as “working the buses,” in which officers would board long-distance buses and request passengers’ permission to conduct a pat-down search. The Florida Supreme Court had found these searches to violate the Fourth Amendment because passengers approached by uniformed police officers in the confines of a bus would not feel “free to leave.” But in Florida v. Bostick, the Supreme Court disagreed, suggesting that to the contrary, a “reasonable person,” advised that he was free to say no, would indeed “feel free to decline the officers’ requests or otherwise terminate the encounter.”

Eleven years later, in United States v. Drayton, the court dispensed with the premise that passengers needed to be informed of their right to say no. That 5-to-4 decision reinstated the convictions of two men who, submitting to a pat-down while on a Greyhound bus, were found to be carrying cocaine taped to their thighs.

There was nothing intimidating about the circumstances of the encounter, Justice Anthony M. Kennedy wrote for the majority, “no overwhelming show of force, no brandishing of weapons, no blocking of exits, no threat, no command, not even an authoritative tone of voice.” Justice Kennedy said it didn’t matter that the passengers were not explicitly informed that they did not have to cooperate. People typically go along with these searches, he asserted, “not because of coercion but because the passengers know that their participation enhances their own safety and the safety of those around them.”

Justice David H. Souter, in dissent, objected that the majority opinion had an “air of unreality.” Indeed.

But let’s look on the bright side. The Supreme Court tells us that if we don’t know our constitutional rights, we have only ourselves to blame. Knowledge of the Constitution, along with other basic elements of civics, is at pathetically low levels: only a quarter of high school seniors — people old enough to vote, or nearly so — demonstrated proficiency in a recent national survey of students’ knowledge of how government works.

So perhaps this week’s decision could be harnessed to provide the motivation evidently missing from the classroom. Students could be instructed that if the police come pounding on their door, and they don’t know enough to stand on their Fourth Amendment rights, they have only themselves to blame.