In the case of Oregon v. Mathiason, the Supreme Court ruled that a suspect being questioned by police in a non-custodial setting is not entitled to Miranda warnings. The defendant, Robert Allen Mathiason, was on parole when he voluntarily went to a police station after being asked for questioning regarding a burglary. He was informed that he was not under arrest and could leave at any time but confessed during this meeting without having been read his Miranda rights. His confession led to his conviction for burglary which he appealed on grounds that it had been obtained unlawfully due to lack of Miranda warning before interrogation. However, the Supreme Court held in favor of Oregon stating that since Mathiason wasn't taken into custody or deprived of his freedom in any significant way prior to or during questioning; hence no violation occurred as per Fifth Amendment's protection against self-incrimination clause.

In the dissenting opinion for Oregon v. Mathiason, Justice Marshall argued that the majority's decision significantly weakened Miranda rights. He contended that a suspect should not be expected to understand their legal situation without being informed of their rights by law enforcement officials. According to him, it was unreasonable to expect an individual in custody and under interrogation to know they were free to leave at any time unless explicitly told so by police officers. Furthermore, he disagreed with the majority's assertion that informing suspects of their freedom would lead to confusion or hinder effective law enforcement practices. Instead, he believed this information was crucial for ensuring fair treatment during interrogations and upholding constitutional protections against self-incrimination.