Immunity of witnesses; record.

Whenever, in the judgment of the United States Attorney for the District of Columbia, the testimony of any witness, or the production of books, papers, or other records or documents, by any witness, in any case or proceeding involving a violation of this subchapter before any grand jury or a court in the District of Columbia, is necessary in the public interest, such witness shall not be excused from testifying or from producing books, papers, and other records and documents on the grounds that the testimony or evidence, documentary or otherwise, required of such witness may tend to incriminate such witness, or subject such witness to penalty or forfeiture; but such witness shall not be prosecuted or subject to any penalty or forfeiture for or on account of any transaction, matter, or thing concerning which such witness is compelled, after having claimed his or her privilege against self-incrimination, to testify or produce evidence, documentary or otherwise; except that such witness so testifying shall not be exempt from prosecution and punishment for perjury or contempt committed in so testifying. The judgment of the United States Attorney for the District of Columbia that any testimony, or the production of any books, papers, or other records or documents, is necessary in the public interest shall be confirmed in a written communication over the signature of the United States Attorney for the District of Columbia, addressed to the grand jury or the court in the District of Columbia concerned, and shall be made a part of the record of the case or proceeding in which such testimony or evidence is given.