The Fifth Amendment (Amendment V) to the United States Constitution is part of the Bill of Rights and protects a person from being compelled to be a witness against themselves in a criminal case. "Pleading the Fifth" is a colloquial term for invoking the right that allows a witness to decline to answer questions where the answers might incriminate him, and generally without having to suffer a penalty for asserting their right. A defendant cannot be compelled to become a witness at his own trial. If, however, they choose to testify, they are not entitled to their right, and inferences can be drawn from a refusal to answer a question during cross-examination. The Amendment requires that felonies be tried only upon indictment by a grand jury. Federal grand juries can force people to take the witness stand, but defendants in those proceedings have Fifth Amendment privileges until they choose to answer any question. To claim the privilege for failure to answer when being interviewed by police, the interviewee must have explicitly invoked the constitutional right when declining to answer questions.
The Amendment's Double Jeopardy Clause provides the right to be tried only once in federal court for the same offense. The Amendment also has a Due Process Clause (similar to the one in the 14th Amendment) as well as an implied equal protection requirement (Bolling v. Sharpe). Finally, the Amendment requires that the power of eminent domain be coupled with "just compensation" for those whose property is taken.
The amendment as proposed by Congress in 1789 reads as follows:
No person shall be held to answer for a capital, or otherwise infamous crime, unless on a presentment or indictment of a Grand Jury, except in cases arising in the land or naval forces, or in the Militia, when in actual service in time of War or public danger; nor shall any person be subject for the same offence to be twice put in jeopardy of life or limb; nor shall be compelled in any criminal case to be a witness against himself, nor be deprived of life, liberty, or property, without due process of law; nor shall private property be taken for public use, without just compensation.