Then what exactly is the Miranda rule? It's an admissibility rule for criminal trial judges. All Miranda ever said was that courts could not admit as evidence of guilt a statement obtained by custodial interrogation, unless the defendant had first been told of his rights and had agreed to waive them and talk. "Miranda conditioned the admissibility at trial of any custodial confession on warning a suspect of his rights." (Missouri v. Seibert) "Miranda itself made clear that its focus was the admissibility of statements." (U.S. v. Patane)
Although it is not unusual to see lower court opinions mistakenly describing a police officer's interrogation as "unlawful" or "unconstitutional" based on a finding that Miranda procedures were not followed, the Supreme Court has been careful to note that it is only the erroneous introduction of a statement in court that violates the Fifth Amendment-not the officer's non-coercive questioning of the suspect.
In Chavez v. Martinez, the Supreme Court ruled that because non-Mirandized questioning is not unlawful or unconstitutional, officers cannot be sued civilly for violating a suspect's Fifth Amendment rights on the basis of such questioning. The court recently reaffirmed this distinction in the Patane case:
"A mere failure to give Miranda warnings does not, by itself, violate a suspect's constitutional rights or even the Miranda rule. Police do not violate a suspect's constitutional rights (or the Miranda rule) by negligent or even deliberate failures to provide the suspect with the full panoply of warnings prescribed by Miranda. Police cannot violate the Self-Incrimination Clause by taking unwarned though voluntary statements."
In other words, although Miranda procedures must be followed in order to ensure the admissibility of custodial statements at trial, they "are not themselves rights protected by the Constitution." (Moran v. Burbine) Therefore, non-coercive questioning that merely fails to meet Miranda's admissibility requirements is not unconstitutional. Because evidence derived from statements obtained without valid Miranda warnings and waivers is not the result of any constitutional violation, the derivative evidence exclusionary rule does not apply.