The United States v. Calandra case in 1973 revolved around the issue of whether a witness could refuse to answer questions before a grand jury based on evidence obtained illegally, invoking the Fourth Amendment's protection against unreasonable searches and seizures. The Supreme Court ruled 6-3 that such exclusionary rule does not apply to grand jury proceedings. The court argued that extending this rule would deter law enforcement and impede the functioning of the grand jury system, which is designed to investigate criminal conduct. Therefore, even if evidence was obtained unlawfully, it can still be used for questioning witnesses during these proceedings.

In the dissenting opinion for United States v. Calandra, Justice Brennan argued that the majority's decision undermined Fourth Amendment protections against unreasonable searches and seizures. He contended that allowing illegally obtained evidence to be used in grand jury proceedings would incentivize law enforcement officers to disregard constitutional rights during investigations. Brennan also disagreed with the majority's assertion that excluding such evidence from grand juries would hinder their investigative functions, arguing instead that it was more important to uphold citizens' constitutional rights than expedite criminal investigations. Furthermore, he expressed concern about potential abuses of power by prosecutors and police officers if they were allowed to use unlawfully seized evidence without repercussions.