In the case of Fisher et al. v. United States et al., 1975, the U.S Supreme Court ruled on issues related to attorney-client privilege and its applicability in tax evasion cases. The court held that documents transferred from a client to an attorney for legal advice could be subpoenaed by the government if they contained evidence relevant to a criminal investigation, even though such documents were protected under attorney-client privilege when in possession of the client. This ruling was based on two main reasons: first, because these documents had been prepared before seeking legal counsel; secondly, since their existence and location were known prior to being handed over to attorneys - thus not considered as privileged communication between lawyer and client.

In the dissenting opinion for Fisher et al. v. United States et al., Justice Marshall, joined by Justice Brennan and Justice Douglas, argued that the majority's decision eroded Fifth Amendment protections against self-incrimination. They contended that compelling taxpayers to surrender their tax documents violated their right not to incriminate themselves because it forced them to admit the existence, possession and authenticity of those documents - all testimonial acts protected by the Fifth Amendment. The dissent also disagreed with the majority's assertion that these were mere physical acts devoid of communicative aspects or testimonial significance; they maintained such an interpretation was too narrow a view of what constituted testimony under this constitutional protection. Furthermore, they expressed concern over potential abuse where prosecutors could use this ruling as a loophole around obtaining warrants or subpoenas for other types of personal records in future cases.