Contradicting previous evidence

(1) Every person who, having given evidence on oath at a preliminary inquiry– (a) wilfully gives at the trial evidence which contradicts the evidence given by him upon the same subject-matter at the preliminary inquiry; or (b) wilfully varies or alters at the trial the evidence given by him upon the same subject-matter at the preliminary inquiry, with intent unlawfully to shield or injure any person, or to deceive the court or to defeat, obstruct or pervert the course of 153 justice, shall be guilty of a misdemeanour punishable either on indictment or summarily, provided that the punishment on summary conviction shall not exceed imprisonment for six months. (2) Upon the trial of any person for a crime under this section, it shall not be necessary to prove the falsity of the evidence given either at the preliminary inquiry or at the trial. (3) No complaint or information for a crime under this section shall be laid without the consent in writing of the Director of Public Prosecutions.