In the case of Blau v. United States (1950), the Supreme Court ruled on an issue related to self-incrimination under the Fifth Amendment. The defendant, Irving Blau, was convicted for contempt of court after refusing to answer questions before a grand jury regarding alleged communist activities, asserting that his responses could incriminate him. On appeal, he argued that his conviction violated his Fifth Amendment rights against self-incrimination. However, the Supreme Court upheld Blau's conviction in a 5-4 decision stating that potential defendants must claim their privilege against self-incrimination in each instance it may be applicable rather than making a blanket assertion of this right at all times and circumstances during questioning by authorities or courts.

In the dissenting opinion for Blau v. United States, Justice Douglas argued that the majority's decision was a departure from established principles of criminal law and procedure. He contended that it is not enough to show mere association with an organization known to advocate violent overthrow of the government; there must be clear evidence showing active participation or personal guilt in such activities. The defendant’s refusal to answer questions about his political affiliations should not be construed as proof of guilt but rather seen as exercising his constitutional right against self-incrimination under the Fifth Amendment. Furthermore, he criticized the use of contempt power by Congress which could potentially lead to abuse and encroach on individual liberties if left unchecked.