Harris v. New York (1971)
The Court said that Miranda did not mean that evidence barred from use during the prosecution's case could not be used for any purpose. They said the Miranda
protection could not be "perverted into a license to use perjury by way
of a defense, free from the risk of confrontation with prior
Michigan v. Tucker (1974)
The Court ruled that the witness could testify. In this case they
made a distinction between a violation of the Fifth Amendment right
against self-incrimination and a mere violation of the Miranda rule. Since the defendant was warned about his right against self-incrimination, the Court allowed the witness to testify.
Oregon v. Elstad (1985)
The Court ruled that admissions made prior to Miranda warnings
must be suppressed, but later statements, if made voluntarily, may be
used in court. "[T]he mere fact that a suspect has made an unwarned
admission does not warrant a presumption of compulsion," Justice
Illinois v. Perkins (1990)
Justice Kennedy, writing for the majority, held that conversations
between suspects and undercover officers are not held in a
"police-dominated atmosphere" and therefore Miranda warnings are not necessary. No coercion was possible because there was no official interrogation.
New York v. Quarles (1984)
The Court said there is a "public safety" exception which applies in
this case. The police officer acted to further public safety and
therefore the statement made by the defendant telling of the location of
the weapon) before his Miranda rights were read to him was admissible in court.