When a person invokes his/her 5th amendment right, he/she is employing the legal right and US Constitutional protection against self-incrimination. The Fifth Amendment to the US Constitution creates a number of rights relevant to both criminal and civil legal proceedings. In criminal cases, the Fifth Amendment specifically guarantees the right to a grand jury, forbids double jeopardy, and protects against self-incrimination.

The idea of self-incrimination concerns the act of exposing oneself generally to a criminal proceeding. This is normally done by making a statement, "to an accusation or charge of crime or to involve oneself or another [person] in a criminal prosecution or the dangers thereof".

Some clear examples of compelled self-incrimination include: instances where the police or other governmental officials use threats of force, violence, or intimidation to obtain a criminal confession. Legal scholars and others consider the Fifth Amendment to be a real guarantee that before depriving a citizen of life, liberty or property, all government agencies of USA will follow fair procedures, i.e. “due process”.

More Info: www.law.cornell.edu