The Council, any committee thereof or any board appointed by the Council for such purpose shall have the power at any time to consider the affairs of any department or the conduct of any officer or employee to be investigated; and for such purpose shall have the power to compel the attendance of witnesses and the production of books, papers and other evidence; and for that purpose may issue subpoenas or attachments which shall be signed by the President of Council or chairperson of the committee or board making the investigation and shall be served by any officer authorized by law to serve such process. The authority making such investigation shall also have the power to consider the testimony to be given under oath which shall be administered by some officer authorized by general law to administer oaths. Any person under such investigation shall have the right of legal counsel.