Miranda v. Arizona

Miranda v. Arizona, 384 U.S. 436 (1966), is a landmark decision of the U.S. Supreme Court in which the Court ruled that law enforcement must warn a person of their constitutional rights before interrogating them when they are in custody, or else the person's statements cannot be used as evidence against them at their trial. Specifically, the Court held that under the Fifth Amendment to the U.S. Constitution, the government cannot use a person's statements made in response to an interrogation while in police custody as evidence at the person's criminal trial unless they can show that the person was informed of the right to consult with a lawyer before and during questioning, and of the right against self-incrimination before police questioning, and that the defendant not only understood these rights but also voluntarily waived them before answering questions.

Miranda was viewed by many as a radical change in American criminal law, because the Due Process Clause was traditionally understood to protect Americans only from certain forms of formal coercion, such as threats of contempt of court. It transformed law enforcement in the United States by making what became known as the "Miranda warning" part of routine police procedure to ensure that suspects were informed of their rights, which came to be known as "Miranda rights". The Miranda warning concept quickly caught on across American law enforcement agencies, who came to call the practice "Mirandizing".

Pursuant to the U.S. Supreme Court decision Berghuis v. Thompkins (2010), a suspect must unambiguously invoke the right to remain silent or to counsel. If the suspect receives and understands the Miranda warnings and then voluntarily makes statements, those statements may be treated as establishing an implied waiver of those rights.