Immunity

State and federal statutes may grant witnesses immunity from prosecution for the use of their testimony in court or before a grand jury. Sometimes, the testimony of one witness is so valuable to the goals of crime prevention and justice that the promise of allowing that witness to go unpunished is a fair trade. For example, a drug dealer's testimony that could help law enforcement to destroy an entire illegal drug-manufacturing network is more beneficial to society than is the prosecution of that lone drug dealer. Although the FIFTH AMENDMENT to the U.S. Constitution grants witnesses a PRIVILEGE AGAINST SELF-INCRIMINATION, the U.S. Supreme Court has permitted prosecutors to overcome this privilege by granting witnesses immunity. Prosecutors have the sole discretion to grant immunity to witnesses who appear before a grand jury or at trial.

States employ one of two approaches to prosecutorial immunity: Use immunity prohibits only the witness's compelled testimony, and evidence stemming from that testimony, from being used to prosecute the witness. The witness still may be prosecuted so long as the prosecutor can obtain other physical, testimonial, or CIRCUMSTANTIAL EVIDENCE apart from the witness's testimony. Transactional immunity completely immunizes the witness from prosecution for any offense to which the testimony relates.

Congressional committees have the power to grant testimonial immunity to witnesses who testify before members of Congress. Congressional investigations into allegations of misconduct—such as the WATERGATE investigations in the 1970s and the IRAN-CONTRA investigations in the 1980s—rely heavily on witness testimony. Whereas prosecutors simply decide whether to grant immunity to a witness, congressional committees must follow more formal procedures. Immunity may be granted only after a two-thirds majority vote by members of the committee. Ten days before the immunized testimony is given, the committee must advise the JUSTICE DEPARTMENT or the INDEPENDENT COUNSEL of its intention to grant immunity.