The Miranda warning has become a familiar concept by anyone who has watched television over the past 40 years. "You have the right to remain silent . . . " Once you become a suspect, the police must give you this warning before continuing with questioning. If you ask for a lawyer, they must stop the interrogation.
In fact, if the police try to question the suspect at a later date, and he then waives Miranda, the U.S. Supreme Court case of Edwards v. Arizona creates a presumption that the waiver was involuntary, and any subsequent statements can be suppressed. This law is in place to prevent the police from bullying someone into waiving his rights.
We've all seen this on cop shows: the suspect invokes Miranda, and the police release him because they "do not have enough to hold him." Then the investigation reveals new evidence that implicates this suspect, and they bring him in again. The suspect then cracks, waives his rights, and talks. The question becomes, does this presumption ever end? Can an invocation of Miranda ever "expire" through a waiver?
The answer is: it depends. On February 24, the US Supreme Court ruled in the case of Maryland v. Shatzer, that a Miranda invocation has an expiration date. In their opinion, a break of at least 14 days provides a sufficient time period for the police to wait before attempting to re-question a suspect who has previously asserted his right to remain silent under Miranda.
If Miranda rights are given and waived, that waiver will be good and any incriminating statements made will be admissible. However, the 14-day waiting period is based on the facts that the suspect will be at liberty, or at least not in police custody, during that period. This even applies to a prisoner who is in general population during that time.
This is an important fact to bear in mind. Just because you asked for a lawyer once, doesn't mean you do not have to "renew" it at a subsequent interrogation. Be sure to speak up and be pro-active. Say to the officers at the very first question: "I continue to stand on my rights under Miranda, and I want a lawyer."