"QUESTION: Doesn't a police officer always have to read me my "Miranda rights" before questioning me?"
ANSWER: No. A "Miranda warning" is required only if a suspect is in custody and the police intend to interrogate the suspect. In other words, both "custody" and "interrogation" have to occur for Miranda rights to kick in. A statement by a person who is not in custody, or a statement made voluntarily rather than in response to police interrogation, is admissible in evidence at trial even though no Miranda warning was given." -From, "The Criminal Law Handbook"