However, in "Wilson v. Arkansas" (1995) the U.S. Supreme Court ruled that a knock-and-announce before entry was a factor that must be considered in reviewing the overall constitutionality of a Fourth Amendment search. After several state attempts to exclude specific categories (e.g. drug crimes) from the knock-and-announce rule, the Supreme Court in "Richards v. Wisconsin" prohibited the policy, and demanded a return to a case-by-case review scenario. The "Richards" Court suggested that the knock and announce rule could be dispensed with only in certain circumstances, for example where police have reasonable suspicion that an exigent circumstance exists. The Court read its earlier "Wilson" opinion to suggest that such circumstances might include those: