If police fail to read a Miranda warning to a person being questioned in custody, the police cannot use self-incriminating information obtained from the person in court, according to the law office of Memphis criminal attorney J. Jeffrey Lee. Cornell University's Legal Information Institute notes that this is one part of the Exclusionary Rule.
The purpose of the Miranda warning is to protect the Fifth Amendment rights of a person in police custody from coercive police tactics, explains the Federal Bureau of Investigation. The Supreme Court created the warning in 1966, in the case Miranda v. Arizona. To prevent coercion, the Supreme Court requires police to inform a person in custody that they have the right to remain silent before interrogating them.
The Law Office of J. Jeffrey Lee indicates that the Exclusionary Rule is the only remedy for a Miranda violation. Even when police fail to Mirandize a person being questioned, the police may nonetheless keep the person in custody and bring charges against him. Individual police officers are not liable for civil damages for failing to provide Miranda warnings.
The Exclusionary Rule is limited. Police must read a Miranda warning only when a person is both in custody and subject to interrogation, states The Law Office of J. Jeffrey Lee. The Supreme Court does not require a Miranda warning if a person makes a statement to police at home or even at a police station if the person is free to leave. Carl Benoit notes that voluntary statements made by an un-Mirandized person in police custody are not subject to the Exclusionary Rule. Thus, the law allows police to use some self-incriminating statements made by a person who has not received a Miranda warning.