Definition : immunity granted to a witness in a criminal case that prevents the use of the witness's compelled testimony against that witness in a criminal prosecution Transactional and use immunity are granted to preserve the constitutional protection against self-incrimination. The states grant either form of this immunity, while the federal government grants only use immunity. A witness with use immunity may still be prosecuted, but only based on evidence not gathered from the protected testimony. 2: a usu. statutory prohibition that excludes specific documents or information from discovery