s the act of refusing to testify under oath in a court of law or any other tribunal (such as a Congressional committee) on the ground that the answers that would be given could be used as evidence against the witness to convict him or her of a criminal offense. Although similar to the right to remain silent when being questioned by law enforcement officers, and coming from the same source, namely the Fifth Amendment in the Bill of Rights, the right to refuse to answer when under oath has a longer history than Miranda rights.
As federal grand juries have the power to subpoena individuals and force them to take the witness stand, defendants in such proceedings invariably refuse to answer any questions put to them, citing their Fifth Amendment rights. If the defendant does answer any question put by the prosecutor during the proceeding, the protection of the Fifth Amendment is lost.citation needed
One famous example of "Plea 5th" in recent history was when Colonel Oliver North was asked to testify before Congress regarding his role in destroying documents during the Iran-Contra Affair.1
North refused to answer on the grounds that his answers would incriminate him.
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