Prosecution of offences under this Act.
(a) within 12 months from the date on which the offence was committed, or
(b) within 6 months from the date on which evidence sufficient, in the opinion of the person instituting the proceedings, to justify proceedings comes to that person’s knowledge,
whichever is later, provided that no such proceedings shall be commenced later than 5 years from the date on which the offence concerned was committed.
(3) For the purposes of this section, a certificate signed by or on behalf of the person initiating the proceedings as to the date on which evidence referred to in subsection (2)(b) came to his or her knowledge shall be evidence of that date and, in any legal proceedings a document purporting to be a certificate under this section and to be so signed shall be admitted as evidence without proof of the signature of the person purporting to sign the certificate, unless the contrary is shown.
(4) It shall be presumed, until the contrary is shown, that proceedings for an offence under this Act were commenced within the appropriate period.