In the case of Jencks v. United States, 1956, Clinton Jencks was convicted for falsely declaring that he was not a member of the Communist Party on his labor union officer's non-Communist affidavit. The conviction relied heavily on testimonies from two FBI informants who claimed to have personal knowledge about Jenck's involvement with the party. However, their reports and statements made to the FBI were withheld during trial despite requests by defense counsel for examination. On appeal, the Supreme Court ruled in favor of Jencks stating that withholding these documents violated his rights under compulsory process clause and due process clause of Sixth Amendment as they could be material for impeachment or contradiction purposes against prosecution witnesses' credibility. This landmark decision led to enactment of "Jencks Act" which allows defendants access to government witness statements after they testify in federal criminal trials.

In the dissenting opinion for Jencks v. United States, Justice Tom C. Clark argued that the majority's decision could potentially compromise national security and disrupt federal law enforcement efforts by requiring disclosure of confidential government reports to defendants in criminal cases. He contended that such a requirement would discourage informants from providing information due to fear of exposure, thereby undermining investigations into organized crime or subversive activities. Furthermore, he expressed concern over potential misuse of these documents by defense attorneys who might use them for purposes unrelated to their client’s case or even publicize sensitive information contained therein. Justice Clark also criticized the majority's reliance on an overly broad interpretation of Brady v Maryland (1963), asserting it was not intended as a general rule mandating full disclosure in all circumstances but rather applied only when there is reasonable probability that withheld evidence would have changed outcome of trial.