Less than two years after ruling that police are generally required to knock and announce their presence before entering a home to conduct a search, the Supreme Court agreed Friday to decide whether to create a blanket exception to that rule when the object of the search is evidence of illegal drug dealing.

The justices accepted an appeal from a ruling by the Supreme Court of Wisconsin that the police "do not have to knock and announce" when they suspect drug dealing and have a warrant to search a home. "Exigent circumstances are always present" under such a scenario, the state court said, given the ease with which the evidence can be destroyed or the suspects can flee.

The Supreme Court's 1995 decision in Wilson vs. Arkansas indicated that unannounced entries could be more easily justified in drug cases than in other types of searches, but suggested that the reasonableness of any entry should be evaluated case by case rather than with a blanket policy.

A half-dozen state courts that have examined the issue after the 1995 ruling have declined to create a general exception for drug searches. The Wisconsin Supreme Court, which had recognized a general exception before the 1995 decision, is alone in adhering to that approach.

The appeal was brought by a man who was convicted in 1992 of dealing cocaine on the basis of evidence the police obtained from his hotel room in Madison, Wis. The police had a search warrant but did not announce their presence to the man, Steiney Richards.

The Wisconsin court's decision last June, upholding the conviction and rejecting Richards' challenge to the search, came over the dissent of Chief Justice Shirley Abrahamson, who said the decision "cannot be squared" with the U.S. Supreme Court's ruling in Wilson vs. Arkansas. The Wisconsin court created an exception that "swallows the rule," she said.

The 1995 decision was written by Justice Clarence Thomas for a unanimous court. Thomas cited English court cases, going back to the early 1600s, to support his conclusion that requiring the police to announce their presence was firmly embedded in the English common law that helped form the views of the framers of the Constitution.

"The common-law knock-and-announce principle was woven quickly into the fabric of early American law," Thomas said.

The decision's conclusion was that the question of whether the police knocked and announced their presence must be part of the analysis of whether a search was "reasonable," within the meaning of the 4th Amendment's prohibition against unreasonable search and seizure.

In the appeal the court accepted Friday, the defendant's lawyer, David Karpe, told the justices that "the law is in great need of clarification as to what reasonableness requires."