The council shall have power to compel the attendance of witnesses and the production of documents and other evidence at any meeting of the body or of any committee thereof, and for that purpose may issue subpoenas and attachments in any case of inquiry, investigation, or impeachment, and cause the same to be served and executed in any part of the Commonwealth, and, if any witness shall refuse to testify as to any fact within his knowledge or to produce any documents within his possession or under his control, the president of the council shall forthwith report the facts relating to such refusal to that one of the courts of common pleas of the proper county to which current new actions and proceedings may at the time be distributed, apportioned, and assigned, and all questions arising upon such refusal and also upon any new evidence not included in said president's report (which other testimony or documents may be offered either in behalf of or against such witness) shall at once be heard by said court. If the court determine that the testimony or document required of such witness is legally and properly competent and ought to be given or produced by him, said court shall make an order commanding such witness to testify or to produce documents (or both as the case may be), and if said witness shall thereafter refuse to testify or to produce documents as aforesaid in disobedience of such order of the court, then the said court shall have power to order the commitment of such witness to the county jail of the proper county for contempt.

No witness shall be excused from testifying in any criminal proceeding or in any investigation or inquiry before the council, before any committee thereof, or before any officer of the city having the right to conduct the investigation, touching his knowledge of any offense committed against the provisions of this article, but such testimony shall not be used against him in any criminal prosecution whatever.