“A lot of people assume that the police are required to read a suspect his Miranda rights upon arrest. That is, they assume that one of a person’s rights is the right to be read their rights. It often happens that way on Law & Order, but that’s not what the law actually requires. The police aren’t required to follow Miranda. Miranda is a set of rules the government can chose to follow if they want to admit a person’s statements in a criminal case in court, not a set of rules they have to follow in every case.“
— Orin Kerr at The Volokh Conspiracy
There’s been a fair amount of misinformation circulated over the past week about Miranda warnings. Lawprof Orin Kerr’s short piece at The Volokh Conspiracy presents a nice summary of the basics, including the effects of not giving the Miranda warning to a suspect.