12.—(1) Subject to paragraph (2) below, summary proceedings for an offence under these Regulations may be commenced in Scotland within a period of 6 months from the date on which evidence sufficient in the opinion of the procurator fiscal to warrant proceedings came to his knowledge.
(2) No such proceedings shall be commenced by virtue of this regulation more than 3 years after the commission of the offence.
(3) For the purposes of this regulation, a certificate signed by or on behalf of the procurator fiscal and stating the date on which evidence sufficient in his opinion to warrant the proceedings came to his knowledge shall be conclusive evidence of that fact.
(4) A certificate stating that matter and purporting to be so signed shall be deemed to be so signed unless the contrary is proved.
(5) Subsection (3) of section 331 of the Criminal Procedure (Scotland) Act 1975 (date of commencement of proceedings)(1) shall apply for the purposes of this regulation as it applies for the purposes of that section.