Final answer:
The Supreme Court case Miranda v. Arizona ruled that an accused must unambiguously invoke their right to an attorney, which police must honor by stopping interrogation until an attorney is present, building upon the rights established in Gideon v. Wainwright.
Step-by-step explanation:
The Supreme Court case that held that an accused who wants to invoke his or her right to an attorney is required to do so unambiguously is Miranda v. Arizona, 384 U.S. 436 (1966).
In this landmark decision, the Court established that police must advise criminal suspects of their rights under the Constitution, which includes the right to remain silent, to consult with a lawyer, and to have one appointed if they are indigent.
Moreover, if a suspect indicates that they wish to remain silent or wants an attorney, the interrogation must cease until an attorney is present.
This case built upon the ruling in Gideon v. Wainwright, which mandated that state courts provide attorneys for defendants who could not afford them, ensuring the right to counsel is observed.