The Patent Act was amended in 1993 to to require that an invention cannot be obvious to the skilled person having regard to information that was publicly available:
28.3 The subject-matter defined by a claim in an application for a patent in Canada must be subject-matter that would not have been obvious on the claim date to a person skilled in the art or science to which it pertains, having regard to
(a) information disclosed more than one year before the filing date by the applicant, or by a person who obtained knowledge, directly or indirectly, from the applicant in such a manner that the information became available to the public in Canada or elsewhere; and
(b) information disclosed before the claim date by a person not mentioned in paragraph (a) in such a manner that the information became available to the public in Canada or elsewhere.
While jurisprudence developed under the pre-1993 Patent Act restricted prior art references for obviousness to those that would have been located by the skilled person after a “reasonably diligent search” (see Illinois Tool Works Inc. v. Cobra Fixations Cie Ltée. – Cobra Anchors Co. Ltd at para 100) it has not been entirely clear whether this test survived the introduction of section 28.3. For example, while the Court of Appeal ultimately held that it did not need to resolve the issue in E. Mishnan v. Supertek, it queried whether the reasonably diligent search test was still applicable under the new Patent Act:
 In Apotex Inc. v. Sanofi-Aventis, 2011 FC 1486,  F.C.J. No. 1813, Boivin J. (as he then was) stated that:
603 […] the prior art must have been publicly available as of the [relevant] date […] – and it must further be locatable through a reasonably diligent search. The burden is on the party relying upon the prior art to establish that it could be found in a reasonably diligent search (Janssen-Ortho Inc. v Novopharm Ltd., 2006 FC 1234, 57 CPR (4th) 6), in this case, Apotex. (emphasis added)
 While this Court disagreed with the conclusion of Boivin J. on obviousness, there was no disagreement expressed in relation to the test for determining what documents would be included as part of the relevant prior art (2013 FCA 186,  F.C.J. No. 856, at paragraph 77). None of the parties in this appeal made any submissions in relation to whether section 28.3 of the Patent Act, R.S.C., 1985, c. P-4 changed the test for determining what documents would be included as part of the relevant prior art. Presumably any submissions based on this section would be that the scope of documents that would be included is broader and would include any information that became available to the public and not just restricted to documents that could be found by conducting a reasonably diligent search. In this case, since I have concluded that based on the test as described above, the Federal Court Judge did not err by including the McDonald Patent as part of the state of the art, there is no need to address the issue of whether section 28.3 of the Patent Act has changed this test.
Mylan Tadalafil FCA
A recent decision of the Federal Court of Appeal sheds some new light on the issue. On April 20, 2016 the Court of Appeal released it Reasons for Judgment in Mylan’s appeal of a prohibition order under the Patented Medicines (Notice of Compliance) Regulations. While the decision mainly dealt double patenting (see our post here), the decision also considered obviousness and specifically what type of references may be cited therefor. While not explicitly addressing the “reasonably diligent search” test, the Court of Appeal held that any publicly available teaching, however obscure or not generally accepted, can render a claim obvious:
 Prior art is the collection of learning in the field of the patent at issue. It comprises any publically available teaching, however obscure or not generally accepted.
 In an obviousness challenge, any piece of prior art, including a collection of works, can be cited as rendering the impugned patent obvious and therefore not patentable: SanofiSynthelabo at paras. 67-71.
A copy of the Court of Appeal’s Reasons in Mylan tadalafil may be found here.