In Yellin v. United States, the Supreme Court ruled in favor of Irving Yellin who was convicted for contempt of Congress after refusing to answer questions from the House Un-American Activities Committee (HUAC). The committee had summoned him based on his alleged affiliation with the Communist Party. However, he argued that HUAC's decision to call him as a witness was influenced by hostility and prejudice against him due to his political beliefs, which violated his right to fair procedure under the Fifth Amendment's Due Process Clause. The Supreme Court agreed with Yellin and overturned his conviction. They found that although HUAC publicly stated they would consider each case individually without bias or preconceived notions about witnesses' affiliations or beliefs, internal communications revealed prejudiced attitudes towards individuals like Yellin suspected of communist ties. This discrepancy between public statements and private actions constituted a violation of procedural fairness guaranteed by due process rights. This ruling reinforced constitutional protections against biased governmental proceedings even during periods marked by intense anti-communist sentiment.

In the dissenting opinion for Yellin v. United States, Justice Harlan argued that the majority's decision to overturn Yellin's conviction was based on a misinterpretation of the law and an overreach of judicial authority. He contended that it was not within the Court’s purview to scrutinize or question Congress' motives in calling witnesses before its committees, as long as there were legitimate legislative purposes behind their actions. Furthermore, he believed that even if some members of Congress had personal biases against Yellin due to his political beliefs, this did not necessarily mean they acted unfairly or violated his rights during his hearing. In essence, Justice Harlan disagreed with the majority's view that subjective factors like bias should be considered when evaluating whether someone received fair treatment under congressional investigations; instead he advocated for focusing solely on objective legal standards and procedures.