In Richards v. Wisconsin (1997) 520 U.S. 385, the court reiterated that knock-notice is a part of the reasonableness inquiry of the Fourth Amendment. The Wisconsin Supreme Court had concluded police officers are never required to knock and announce when executing a search warrant in a felony drug matter because of the inherent risks and the potential for destruction of evidence. (520 U.S. at pp. 388-392.) In rejecting this per se approach, the federal high court explained the circumstances of a given search may nullify the concerns expressed by the Wisconsin Supreme Court: "While drug investigation frequently does pose special risks to officer safety and the preservation of evidence, not every drug investigation will pose these risks to a substantial degree. For example, a search could be conducted at a time when the only individuals present in a residence have no connection with the drug activity and thus will be unlikely to threaten officers or destroy evidence. Or the police could know that the drugs being searched for were of a type or in a location that made them impossible to destroy quickly. In those situations, the asserted governmental interests in preserving evidence and maintaining safety may not outweigh the individual privacy interests intruded upon by a no-knock entry." (520 U.S. at p. 393.) The United States Supreme Court held that the Fourth Amendment does not permit a blanket exception to the knock-and-announce requirement for search warrants issued for felony drug investigations. The Court held a no-knock entry to effectuate a search warrant was justified if police have a reasonable suspicion knocking and announcing their presence would be dangerous or futile, or knocking and announcing would inhibit the effective investigation of the crime by allowing the destruction of evidence.