In Maryland v Shatzer, the US Supreme Court set a bright-line rule regarding the time period that must elapse before the police may re-question a suspect who has previously invoked Miranda. The police must wait 14 days before re-questioning, assuming the suspect is at liberty, meaning not in police custody. However, general population in prison is not considered in custody, and even those in prison can be re-questioned following the 14 day period if in gen pop.
This case marks the first time that the Court set a threshold time requirement in this context. Prior to this holding, the invocation of Miranda by a suspect precluded the police from further questioning regarding the subject offense or any others. This included situations where a suspect subsequently waived his rights prior to questioning on the subsequent occasion. This ruling fundamentally changed the law and gives the police an opportunity for another bite at the apple, but still requires that the suspect knowingly and intelligently waive those rights in connection with the later questioning.