In Kastigar et al. v. United States, the Supreme Court ruled on whether a witness could be compelled to testify over his claim of Fifth Amendment protection against self-incrimination if he was granted immunity from prosecution for the matters about which he was forced to testify. The court held that such testimony is indeed constitutionally permissible under the Fifth Amendment's self-incincrimination clause as long as it comes with immunity from prosecution that is coextensive with the scope of the privilege itself - meaning, essentially, full or "transactional" immunity rather than mere "use and derivative use" immunity (which only protects a witness from their own testimony being used against them directly). This decision clarified and established an important principle regarding testimonial compulsion in American jurisprudence: while individuals cannot be prosecuted based on their immunized testimonies, they can still potentially face legal consequences for related actions not covered by said immunities.

In the dissenting opinion for Kastigar et al. v. United States, Justice Thurgood Marshall argued that the majority's decision to uphold a federal statute allowing prosecutors to compel testimony from witnesses granted immunity from prosecution was unconstitutional. He contended that this violated an individual's Fifth Amendment right against self-incrimination and undermined their fundamental rights as citizens. The justice believed that such compelled testimonies could potentially be used in criminal prosecutions indirectly, which would infringe upon constitutional protections even if not directly utilized in court proceedings. Furthermore, he expressed concern over how effectively courts could monitor or prevent indirect uses of such information by law enforcement agencies and prosecutors' offices across different jurisdictions due to practical difficulties involved therein.