Part of the Federal Criminal Code [18 U.S.C. 6005] establishes a process for congressional committees to follow in order to grant "use" immunity to potential witnesses. "Use" immunity protects witnesses from future criminal prosecution based on any information contained in their testimony before Congress. This means witnesses can offer testimony which implies, or even reveals, their guilt without fear of prosecutors using it against them. However, prosecutors could still seek a criminal conviction against the witnesses based on other evidence or another witness's testimony.

When a witness exercises his/her Fifth Amendment right against self-incrimination, the granting of immunity may produce testimony, but it is often at the cost of full legal accountability for criminal conduct. In seeking immunity, congressional committees must balance the need for factual evidence with the impact on the outcome of legal proceedings. This balancing act is well-described in a Missouri Law Review article by Charles Tiefer and George Van Cleve, "Navigating the Shoals of Use Immunity" (MLR, vol. 55, pp. 43-92, 1990.)

The process for granting "use" immunity begins when a congressional committee votes on whether or not to pursue immunity for a specific witness. Two-thirds of committee members must vote in support. The two-thirds vote requirement means that neither the majority nor the minority members of a committee can act alone to pursue an immunity grant.

After a successful vote, the committee must inform the Attorney General of the United States of its intent to seek immunity. The committee then asks a U.S. District Court to issue an order requiring a certain witness to testify or provide the requested information under grant of immunity. The District Court consults with the Attorney General on the matter, and the Attorney General may request a delay of up to 20 days to investigate the legal implications of the request.

The best known recent examples of immunity granted by Congress occurred in 1973, when immunity was granted John Dean, White House Counsel, during the Watergate Hearings; and 1987, when Oliver North and John Poindexter, the President's national security adviser, were both granted immunity during the Iran-Contra Hearings. These grants of immunity resulted in a limited conviction for John Dean, and a reversal of conviction for Oliver North and John Poindexter. Most recently, in September 1997, the Senate Governmental Affairs Committee granted immunity to a group of Buddhist nuns in exchange for their testimony during its campaign finance hearings.