A federal judicial doctrine that operates to exclude from evidence a confession that is obtained from a person who was not brought before a judicial officer promptly after the person's arrest.
The McNabb-Mallory rule, which is applicable only in federal prosecutions, derives from the U.S. Supreme Court cases of McNabb v. United States, 318 U.S. 332, 63 S. Ct. 608, 87 L. Ed. 819 (1943), and Mallory v. United States, 354 U.S. 449, 77 S. Ct. 1356, 1 L. Ed. 2d 1479 (1957). The McNabb-Mallory rule is not a constitutional rule but is based on federal law and on the federal judiciary's authority to oversee the administration of criminal justice within the federal courts. The purpose of the rule is to provide protection against an arresting officer's "secret interrogation" of a suspect prior to the suspect's appearance before a judicial officer. Before McNabb, authorities could effectively and without penalty delay a suspect's presentment before a judicial officer in order to obtain a confession. McNabb held that the penalty for obtaining confessions as a result of such a delay is the exclusion of the confession at trial.
In McNabb, a federal revenue agent was killed when agents attempted to arrest members of the McNabb family, a clan of Tennessee mountaineers. The agents subsequently arrested three of the McNabbs and placed them in a detention cell for more than fourteen hours. Over the course of the next two days, federal agents interrogated the McNabbs and finally obtained confessions from them. Based primarily on these confessions, which were admitted into evidence at trial, a jury convicted the McNabbs of second-degree murder. On appeal, however, the U.S. Supreme Court held that the McNabbs' confessions should have been excluded from trial because the federal agents had improperly obtained the confessions by delaying their appearance before a judicial officer. A federal law at the time required federal law officers to take a person charged with any crime before the nearest U.S. commissioner or judicial officer. Relying on this law and on the Court's supervisory authority to oversee justice in the federal court system, the Court held that the confessions should have been excluded from evidence at trial. The Court noted in its decision that the arresting officers had "subjected the accused to the pressures of a procedure which is wholly incompatible with the vital but very restricted duties...