At common law, the rules of evidence applied to exclude involuntary confessions on grounds of unreliability.
In 1936, the Supreme Court recognized that the Due Process Clause prevented state police from interrogating defendants in coercive ways so as to produce involuntary confessions that were not the product of a person’s “free will.”
In 1964, the Supreme Court recognized that a defendant’s right to counsel protected an indicted defendant against indirect and surreptitious interrogations as well as those conducted in police stations. The Sixth Amendment right to counsel attaches at the initiation of “adversary judicial proceedings” and applies to all “critical stages” that occur during a “criminal prosecution” until it ends at the sentencing stage.
In 1964, the Supreme Court applied the Fifth Amendment to the states, and, in 1966, the Supreme Court applied the Fifth Amendment to custodial interrogations by state and federal officials.