Answer:
The case in which the Supreme Court ruled that police must inform criminal suspects of their legal rights upon their arrest was Miranda v. Arizona.
Explanation:
In 1963, Ernesto Arturo Miranda was arrested for robbery, kidnapping and sexual assault. He was interrogated by the police and immediately confessed. During the trial, the prosecutor only offered Miranda's confession as evidence. Miranda was found guilty of kidnapping and sexual assault, and sentenced to 20 to 30 years in prison. Miranda's lawyer appealed to the Arizona Supreme Court, but was dismissed. Then he appealed to the Supreme Court.
President Earl Warren, a former prosecutor, announced the court's verdict: Due to the compulsive nature of police interrogations, no confession can be granted unless the suspect has previously been instructed about his rights as set forth in the 5th and 6th Amendments to the Constitution. Accordingly, Miranda's sentence was overturned.
After the verdict, police officers nationwide were trained to educate suspects of their rights when arrested. This obligation to provide information is known today as the Miranda Warning.
