Knock, knock. Who's there? Evidently not the police.

My reply to Robert Spencer's latest ripose to my Islamophobia columns is coming up later today, but in the meantime, here is my Boston Globe column (with links added) on a problem closer, literally, to home: the recent Supreme Court ruling on the legality of no-knock searches. My perspective diverges from both the conventional civil liberatarian view, which enshrines the exclusionary rule as a deterrent and antidote to police misconduct, and from the standard conservative view which tends to idolize the police.

EARLIER this month, the Supreme Court came down with a ruling that some see as a step toward a police state and others as a common-sense approach to justice. In Hudson v. Michigan, the court ruled 5-4 that if the police enter a suspect's home without knocking, this does not make the search unconstitutional.

The majority emphasized that it was not giving a stamp of approval to no-knock searches. While the rule requiring the police to knock, announce themselves, and wait briefly before entering a residence is not part of the Fourth Amendment (which protects citizens from unlawful searches), this procedure has long been a part of common law. What the court held was that a violation of this rule -- unlike, say, a search without a proper warrant -- is not serious enough to require throwing out the evidence found in the search and letting the defendant go free.

Writing on Slate.com, Akhil Reed Amar, professor of constitutional law at Yale University and former law clerk to Justice Stephen Breyer (one of the dissenters in Hudson), argues that the case raises larger questions about enforcing Fourth Amendment rights. Like the "knock and announce" rule for police entry, the exclusionary rule, which requires dismissal of improperly obtained evidence in a criminal case, is not in the Constitution. As Amar notes, it was not envisioned by the Founding Fathers and was not used by American courts for nearly a century after the Bill of Rights was written. In 1961, in Mapp v. Ohio, the Supreme Court made it the law of the land.

Justice Antonin Scalia's majority opinion in Hudson is broadly critical of the exclusionary rule as a remedy for illegal searches. While Justice Anthony Kennedy joined the majority, he wrote a separate opinion that stressed that the reasoning in this case should apply only to no-knock but otherwise valid searches, with no effect on the exclusionary rule in general.

Scalia's critique makes some excellent points. If the police conduct an illegal and even abusive search -- for instance, trashing the house and roughing up the residents -- the exclusionary rule per se does not punish the bad cops or compensate their victims. The only "reward" for individuals whose rights are violated is that the evidence from an unlawful search cannot be used against them. And if the search uncovers no evidence of guilt -- if the person is innocent -- the exclusionary rule offers no benefits.

The exclusionary rule creates other problems in the justice system. True, cases of murderers and rapists going free because the evidence is dismissed on the proverbial technicality are fairly unusual. What's far more common is police officers lying to cover up technical improprieties in a search, and judges accepting these lies so as to avoid dismissing valid and reliable evidence. But as a result, public confidence in police credibility can be severely undermined. And sometimes -- as in the O.J. Simpson case, when the police entered Simpson's house without a warrant on the blatantly false pretext of being concerned for his safety -- this lack of credibility can lead the jurors to suspect a frame-up.

Yet there is a major problem with Scalia's reasoning. He argues that while 50 years ago abusive police tactics were common and few remedies were available, the situation today is markedly different: Police forces are much more respectful of citizens' rights, and there are far more recourses to civil rights litigation. Yet, writing on the website of Reason magazine, editor Tim Cavanaugh notes that there has been an opposite trend toward increasingly militarized police forces and military-style raids -- particularly in drug cases. In Mississippi, a man named Cory Maye now sits on death row for shooting a police officer whom he mistook for an intruder during a no-knock nighttime raid on his house, in search of drugs on what was apparently a false tip.

Scalia maintains, as does Amar, that civil litigation against the police is the best way to protect the rights of the innocent. But this can also let the police off the hook if they have violated the rights of someone who is guilty: A jury is unlikely to sympathize with a criminal. In such cases, perhaps judicial review boards to assess damages and penalties are a good answer.

Meanwhile, leaving the exclusionary rule intact but exempting no-knock searches from its scope sends the dangerous message that for the police to burst into a citizen's house unannounced is no big deal.

I don't think that "no-knock, no-announce, no-wait" police searches are a trivial matter in a liberal, individual rights-based society. I don't think police professionalism and respect for civil rights in the USA today are everything Scalia seems to believe. (See, for instance, this article by St. Petersburg Times columnst Robyn Blumner.) And, as I said in my column, I think it could be very difficult for a suspect who is guilty, or even a suspect with a police record, to obtain redress against an illegal police search. At the same time, if a murder case was dismissed because the search that yielded the bloody knife was conducted without a knock, I'd be pretty outraged. So maybe it's time to think of other remedies, such as police misconduct review boards that could assess penalties for violators.

Of course, the other issue here is that most cases involving questionable searches are not about murder, rape, or other crimes of violence; they're about drugs. I'm not as gung-ho on drug legalization as some of my libertarian pals, but it's very hard to disagree with the proposition that the War on Drugs is eviscerating our civil liberties -- more so than the War on Terror, for a much longer time, and with a far less compelling reason.