Persons compelled to testify; immunity ACTIVE

Upon the trial of any indictment or information, charging the crimes of attempt to commit sabotage or conspiracy to commit sabotage, no person otherwise competent as a witness shall be disqualified or excused from testifying, concerning the offense charged, on the grounds that the testimony may incriminate himself; but no prosecution can afterwards be had against him concerning the matters upon which he has testified except for perjury in giving the testimony, or contempt of court based upon the giving or refusing to give or the producing or refusing to produce testimony or documents.