In Sims v. United States (1958), the Supreme Court ruled in favor of petitioner, Sims, who was convicted for failing to answer questions during a congressional hearing on allegations of communist infiltration into labor unions. The court held that since the committee had not specifically overruled his objections or clearly apprised him of the consequences of refusal, he could not be punished for contempt under 2 U.S.C.A §192. This decision emphasized that witnesses before Congressional committees have rights which must be respected and cannot be penalized without clear warning about potential repercussions for non-compliance with questioning.

In the dissenting opinion for Sims v. United States, Justice Harlan argued that the majority's decision to reverse and remand was based on a misinterpretation of Rule 52(b) of the Federal Rules of Criminal Procedure. He believed that this rule should only be invoked in exceptional circumstances where an error seriously affects substantial rights or results in a miscarriage of justice. In his view, neither condition applied to this case as there was no evidence suggesting that petitioner's counsel had objected at trial to any alleged errors regarding jury instructions about intent and knowledge related to tax evasion charges. Furthermore, he contended that even if such objections were made and erroneously overruled by the trial judge, it would not have constituted plain error under Rule 52(b). Therefore, he disagreed with reversing conviction solely because appellate courts might perceive some possible prejudice against defendants due to ambiguous jury instructions.