In the Simmons v. United States case of 1967, the U.S Supreme Court ruled that a defendant's testimony given to repudiate evidence obtained through an illegal search cannot be used against them in a subsequent criminal proceeding. The case arose when federal agents illegally seized evidence from petitioner Richard Lloyd Simmons' home without a warrant and subsequently charged him with bank robbery. In order to challenge the admissibility of this evidence, Simmons testified at his pretrial hearing about his ownership of said items which were later used as self-incriminating evidence during trial proceedings leading to his conviction. On appeal, the Supreme Court reversed this decision stating it was unfair for defendants to choose between their Fifth Amendment right against self-incrimination and their Fourth Amendment right against unreasonable searches and seizures.

In the dissenting opinion for Simmons v. United States, Justice Harlan argued that the majority's decision to allow defendants to testify on a limited basis about ownership of seized evidence without opening themselves up to cross-examination on unrelated matters was an unwarranted departure from established legal principles. He contended that this ruling would lead to confusion and inconsistency in future cases because it blurred the line between testimonial and non-testimonial statements made by defendants during trials. Furthermore, he expressed concern over how this new rule could be applied fairly across different situations given its subjective nature. In his view, allowing such selective testimony undermined the prosecution’s right to challenge credibility through cross-examination and compromised trial fairness overall.