33   Certificate not to be disputed unless notice given

(1)  Where a copy of a certificate given by an analyst under this Act has been served upon a defendant who is charged with the commission of an offence against the provisions of this Act or the regulations it shall not be competent for the defendant upon the hearing of the charge to dispute the accuracy of any statement contained in the certificate unless within seven clear days after service upon the defendant of the copy of the certificate the defendant has notified the Director-General by letter forwarded by registered post that the accuracy of the certificate will be disputed at the hearing of the charge.

(2)  Service of the copy of a certificate may be proved in the same manner as service of the summons.