<P> In 1920, the U.S. Supreme Court adopted the "fruit of the poisonous tree" doctrine in the case of Silverthorne Lumber Co. v. United States . The Court stated that allowing evidence gathered as an indirect result of an unconstitutional search and seizure "reduces the Fourth Amendment to a form of words". </P> <P> Wolf v. Colorado 338 U.S. 25 (1949) ruled that states were not required to adopt the exclusionary rule . Despite the ruling, some states adopted the exclusionary rule . In 1955, the Supreme Court of California ruled in People v. Cahan that the exclusionary rule applied for cases in the state of California . By 1960, 22 states had adopted the rule without substantial qualifications: California, Delaware, Florida, Idaho, Illinois, Indiana, Kentucky, Mississippi, Missouri, Montana, North Carolina, Oklahoma, Oregon, Rhode Island, Tennessee, Washington, Texas, West Virginia, Wisconsin, Wyoming . Michigan also had an exclusionary rule, but with limitations for some narcotics and firearms evidence . In Alabama, Maryland, and South Dakota, the exclusionary rule applied in some situations . </P> <P> It was not until Mapp v. Ohio in 1961 that the exclusionary rule was also held to be binding on the states through the Fourteenth Amendment, which guarantees due process . Up until Mapp, the exclusionary rule had been rejected by most states . </P> <P> In 2016, Utah v. Strieff dealt with the exclusionary rule and outstanding warrants and was viewed to be generally favorable towards police . </P>

The case that made the exclusionary rule applicable to the states is