Court Eases 'No Knock' Search Ban

"Resort to the massive remedy of suppression of evidence of guilt is unjustified," Scalia wrote.

Scalia argued that the law enforcement landscape has changed dramatically since 1961, when the Supreme Court first imposed an exclusionary rule on the states to protect against warrantless searches. Today's police are more professional than those of 45 years ago, he observed, and there is "increasing evidence that police forces across the United States take the constitutional rights of citizens seriously."

In this environment, Scalia argued, lawsuits and administrative proceedings are enough to ensure that police comply with the "knock and announce" rule.

That line of reasoning prompted a 30-page dissenting opinion from Justice Stephen G. Breyer, who disputed Scalia's upbeat view of modern policing and argued that lawsuits and police discipline have already proved inadequate to punish and deter "knock and announce" violations.

"Today's opinion," Breyer wrote in dissent, "weakens, perhaps destroys, much of the practical value of the Constitution's knock-and-announce protection." Justices John Paul Stevens, David H. Souter and Ruth Bader Ginsburg joined Breyer.

Scalia's cost-benefit analysis could be invoked not only to deny a new exclusionary rule in this case, Breyer argued, but also to roll back the use of the exclusionary rule to enforce the Fourth Amendment in areas where it has long been recognized.

"The majority's 'substantial social costs' argument is an argument against the Fourth Amendment's exclusionary principle itself," Breyer wrote. "And it is an argument that this Court, until now, has consistently rejected."

Kennedy tried to diminish the apparent sweep of Scalia's opinion, indicating that "the continued operation of the exclusionary rule as settled and defined by our precedents, is not in doubt."

There was strong circumstantial evidence that, if O'Connor had not been replaced by Alito, Breyer would have been speaking for the court.

In January, when the justices heard the case and cast tentative votes, Connor was still on the court. Her comments at argument suggested she favored Breyer's view.

But after she left the court Jan. 31, the court announced the case would be reargued -- a sign that it had reverted to a 4 to 4 tie without her vote.