Section 4. Examination of witnesses.

Any 1[officer or authority] making an enquiry under this Act may examine orally any person supposed to be acquainted with the matter under enquiry or any fact relevant thereto, and may reduce into writing any statement made by the person so examined. Such person shall be bound to answer truly all questions relating to such matter put to him by such 1[officer or authority] other than questions the answers to which would have a tendency to expose him to criminal charge or to a penalty or forfeiture. No such statement, when taken in the absence of a public servant whose conduct is under enquiry, shall be used as evidence against such public servant in any judicial proceeding.