In the United States v. Mandujano case of 1975, the Supreme Court examined whether a grand jury witness could be prosecuted for perjury based on false statements made during testimony, even if he was not advised of his constitutional rights against self-incrimination (Fifth Amendment) and to counsel (Sixth Amendment). The defendant, Benito Mandujano, had been called before a grand jury investigating drug trafficking and lied under oath about his involvement in selling heroin. He argued that since he wasn't informed of his rights prior to testifying, any incriminating evidence should be suppressed. However, the court held that there is no requirement to inform a grand jury witness about their constitutional protections unless they are in custody or deprived of freedom in some significant way. Therefore it upheld Mandujano's conviction for perjury as lying under oath undermines the integrity of judicial proceedings.

In the dissenting opinion for United States v. Mandujano, Justice Brennan, joined by Justices Stewart and Marshall, argued that the majority's decision undermined Fifth Amendment protections against self-incrimination. They contended that a witness before a grand jury should be fully informed of their constitutional rights to remain silent and have legal counsel present during questioning. The dissenting justices believed that Mr. Mandujano was not adequately advised of his rights before testifying in front of the grand jury which led him to make incriminating statements without understanding he could refuse to answer or request an attorney’s presence. They also disagreed with the majority's view on perjury charges; they held it is unfair to charge someone with perjury when they were not properly informed about their right against self-incrimination beforehand because such circumstances may lead individuals into traps where they either admit guilt or lie under oath unknowingly committing another crime.