In the case of Ker et ux. v. California, 1962, the U.S Supreme Court was tasked with determining whether evidence obtained through a warrantless search could be used in court proceedings. The defendants were convicted for possession of marijuana based on evidence seized during a warrantless search by state law enforcement officers who had probable cause but did not have exigent circumstances to justify their actions. The defense argued that this violated their Fourth Amendment rights against unreasonable searches and seizures. The Supreme Court upheld the convictions in a 5-4 decision, ruling that states are not required to exclude evidence obtained through an unlawful search or seizure under federal law (the exclusionary rule). Instead, they should consider whether such action is reasonable under their own laws and constitutions. This marked one of the first times where "reasonable" police conduct was considered sufficient justification for bypassing traditional Fourth Amendment protections.

In the dissenting opinion for Ker et ux. v. California, Justice Douglas argued that the majority's decision violated Fourth Amendment protections against unreasonable searches and seizures. He contended that police officers should not be allowed to forcibly enter a private residence without a warrant unless there is clear evidence of imminent danger or destruction of evidence - conditions he did not believe were met in this case. Furthermore, he criticized the majority's reliance on state law rather than federal constitutional standards to justify their ruling, asserting that it undermined uniformity in interpreting and applying the Constitution across states. Finally, Justice Douglas expressed concern about potential abuses of power by law enforcement if such broad exceptions to warrant requirements were permitted.