To fans of television cop dramas, the Miranda warning has a familiar ring:
"You have the right to remain silent. Anything you say can and will be used against you in a court of law."
It goes on: "You have the right to an attorney. If you cannot afford an attorney, one will be provided for you."
Miranda rights have been read to nearly all persons arrested in the United States since 1966 — but because of one critical exception, they won't be read to the suspect in the Boston Marathon bombing.
Fifth and Sixth Amendment rights
In 1966, the U.S. Supreme Court issued a groundbreaking ruling in the case of Miranda v. State of Arizona.
That ruling found that the Fifth and Sixth Amendment rights of Ernesto Arturo Miranda had been violated after he was arrested and tried for rape and kidnapping. [Understanding the 10 Most Destructive Human Behaviors]
The Fifth Amendment protects an arrested person from being compelled to be "a witness against himself," or self-incrimination; the Sixth Amendment guarantees that a person shall "have the assistance of counsel for his defense."
Miranda signed a confession after hours of interrogation by the Phoenix Police Department. At no point was he informed of his right to remain silent or his right to an attorney.
Miranda rights have undergone significant changes over the years, and some jurisdictions have their own variations of the standard Miranda verbiage.
Many U.S./Mexico border states, for example, have added the following: "If you are not a United States citizen, you may contact your country's consulate prior to any questioning."
The public-safety exception
An important exception was added in 1984, when the U.S. Supreme Court found, in New York v. Quarles, that if public safety is at immediate risk, a suspect's statements are admissible in court, even if his or her Miranda rights have not been explained.
In that case, an arresting officer asked a suspect where his gun was, to which the suspect replied, "The gun is over there." His statement was ruled admissible in court because the presence of a gun constituted a risk to the public.
This so-called "public-safety exception" to Miranda rights has been invoked many times since 1984, most prominently in cases of terrorism.
Boston Marathon bombing suspect Dzhokhar Tsarnaev will be questioned without being read his Miranda rights, according to Slate.
"The legal argument for the [public-safety] exception is that in times of exigency, where the public might be in danger, it is possible to interrogate an individual at some level in order to relieve the public of the danger," former U.S. Attorney General John Ashcroft told NPR.
However, Ashcroft said, "You don't want to get evidence that would be very valuable — maybe essential to a conviction — which is excluded based on the fact that a Miranda warning was not given, or improperly given."
Stating your silence
In 2010, the U.S. Supreme Court ruled in the case of Berghuis v. Thompkins that a defendant had to explicitly state his or her desire to remain silent in order to be protected against self-incrimination.
During a lengthy police interrogation in 2000, murder suspect Van Chester Thompkins remained silent for several hours, until he made some incriminating statements.
But because Thompkins did not specifically state his intention to remain silent, his statements were ruled admissible.
In her dissent, Justice Sonia Sotomayor called the ruling "a substantial retreat from the protection against compelled self-incrimination," the Associated Press reports.