Answering of incriminating questions and certificate of indemnity.

(1) No witness shall be excused from answering any question as to any matter relevant to a matter in issue in the trial of an election petition upon the ground that the answer to such question may criminate or tend to criminate him, or that it may expose or may tend to expose him to any penalty or forfeiture; Provided that— (a) a witness who answers truly all questions which he is required to answer shall be entitled to receive a certificate of indemnity from the prescribed authority; and (b) an answer given by a witness to a question put by or before the prescribed authority shall not, except in the case of any criminal proceeding for perjury in respect of the evidence, be admissible in evidence against him in any civil or criminal proceeding.