In the summer of 1966, the Supreme Court ruled that as a part of your 5th amendment protections, Law enforcement is required to advise you and to insure that you clearly state that you understand that you have certain rights, among which are the right to remain silent.
Most of us rarely consider how important that is, nor do we consider that before 1966, Police could in fact, elicit a "confession" from a suspect from virtually anything that is said. Silence is the best course, and the Police cannot force you to say anything.
So since this has been the case since 1966 (the last 56 years), what happens when a Police Officer fails to insure that a suspect is properly advised of his rights, obtains something like a confession and then gives that tot he Prosecuting authorities? You might think that they would say, "You can't do that..."
But our hyper-willingness to get a conviction at all costs, usually via a plea deal, has led to some interesting actions that have found their way to the US Supreme Court.
And... according to some... MIGHT result in the end of the process of Miranda...