In Callahan v. United States (1931), the U.S Supreme Court ruled on a case involving the Fourth Amendment, which protects against unreasonable searches and seizures. The defendant, Callahan, was convicted for possessing alcohol during Prohibition after police officers found liquor in his home without a search warrant. He appealed to the Supreme Court arguing that this violated his Fourth Amendment rights. However, the court upheld his conviction with a 7-2 majority decision stating that since he had voluntarily let them into his house and did not object when they began their search, it was not an illegal seizure of evidence under the exclusionary rule - which prohibits illegally seized evidence from being used in court trials.

In the dissenting opinion for Callahan v. United States, Justice Stone argued that the majority's decision to uphold a search warrant based on evidence obtained through wiretapping violated Fourth Amendment protections against unreasonable searches and seizures. He contended that wiretapping constituted an invasion of privacy, regardless of whether it was conducted with or without physical trespass into a private space. Furthermore, he asserted that allowing such evidence to be used in court would encourage law enforcement officers to disregard constitutional rights in their investigations. For these reasons, Justice Stone believed the intercepted communications should have been excluded from trial as they were obtained unlawfully.