21. Any person failing or refusing, without just cause, to satisfactorily answer all questions as to which a discovery may be sought, within the time mentioned in section 18 or such extended time as the judge may allow, or to render any testimony in virtue of this act, shall be deemed to be in contempt, and punished accordingly; but no answer given by any person so heard as a witness may be alleged against him in any prosecution under this division or any other act of the Legislature, if the judge has given him a certificate establishing that he has claimed the right to be excused from answering, for the reason above given, and has given full and truthful answers, to the satisfaction of the judge.
R. S. 1964, c. 173, s. 21.