The U.S. Supreme Court has ruled that police can try again to question a suspect who's invoked his Miranda rights if two weeks or more have passed. The case in question involved a suspect who was questioned two years after he originally invoked Miranda. He made some incriminating remarks during that second go. A lower court originally ruled those remarks inadmissible, saying the original Miranda invocation still held. The Supremes disagreed.
Hat Tip: Many thanks, cripjak!