It was thought until quite recently that any applicant for a Canadian patent had to disclose in his specification the best mode then known of working his invention (Minerals Separation North American Corp. v. Noranda Mines Ltd.,  Ex. C.R. 306, rev’d (1952) 69 R.P.C. 81 (P.C.)). Then came Sanofi-Aventis Canada Inc. v. Apotex Inc., 2009 FC 676 to dispel this illusion.
Paragraph 27(3)(c) of the Patent Act provided that a specification must “in the case of a machine, explain the principle of the machine and the best mode in which the inventor has contemplated the application of that principle”. That, said the court, meant that any duty to disclose the best mode of working was excluded from non-machine inventions. So if, as in Sanofi-Aventis, the invention was a new medicine, the inventor need disclose only his second- or third-best modes of working it and keep his best mode to himself.
The Federal Court of Appeal approved Sanofi-Aventis in 2010 in Novopharm Ltd. v. Pfizer Canada Inc., 2010 FCA 242 (rev’d on other grounds sub nom. Teva Canada Ltd. v. Pfizer Canada Inc., 2012 SCC 60), and the restricted view of the best mode duty was recently reaffirmed in Teva Canada Ltd. v. Novartis AG, 2013 FC 141.
In a paper being completed for publication in the Intellectual Property Journal later this year, I argue that this revisionism is wrong and that, despite the recent decisions, the best mode duty continues to apply to all patented inventions in Canada. That duty comes from paragraph 27(3)(a) of the Patent Act, which requires a specification to “correctly and fully describe the invention and its operation or use as contemplated by the inventor.” The duty to disclose the invention’s best mode of being worked is deduced from the comprehensive duty to describe the invention’s operation or use. The best-mode-for-machines provision in paragraph (c) is a special provision that is not intended to detract from or impliedly repeal the duty in paragraph (a).
Sanofi-Aventis did not cite or analyze paragraph 27(3)(a) in its decision. It and the decisions following it were therefore decided per incuriam and may be overruled by the Federal Court of Appeal or simply ignored by the provincial courts.
The paper traces the long history of paragraph 27(3)(a) from its genesis in the language of the 18th century British patent grant. This required the inventor to “particularly describe and ascertain the nature of his invention, and in what manner the same is to be performed.” British courts consistently interpreted this language as requiring the inventor to make a full, frank, and honest disclosure, and that included the best mode of working his invention. The public was entitled to be put in possession of all the inventor knew about the workings of the invention so that, when the patent expired, the public could work it to the same beneficial extent as the inventor could at the time the specification was filed. If the inventor shirked in his duty to disclose, the patent was void.
The obligation came most clearly into American patent law in the U.S. Patent Acts of 1793 and 1836. Their language was copied in the 1830s by the Canadian maritime colonies and the first Canadian Patent Act of 1869. The U.S. Acts included not only a primary duty to describe the invention in “full, clear and exact terms” but also a special provision for machine inventions – the mainstay of the Industrial Revolution – which required the “several modes” of applying the machine’s principle to be given. In 1870 that provision was amended to become a duty to disclose the “best mode” of applying the machine’s principle. Throughout it was recognized that the special duty for machines did not affect the primary duty for all inventions to have their best mode of being worked disclosed. The duty was explicitly applied to all inventions in the U.S. patent revision of 1952, which simply confirmed the prior law, although the most recent amendments to U.S. patent law watered the provision down to a mere talking point with the patent examiner instead of a ground of invalidation.
Canada’s position reflects the U.S. position before these amendments. Although European patents lack a best mode requirement, many Commonwealth jurisdictions retain it and an international trend may favour it, especially among developing nations.
The Supreme Court of Canada nevertheless rightly said in 1981 of subsection 27(3)’s forerunner that it was not “happily phrased” and that certain additions made to it in 1935 added nothing “of substance” to the prior law since 1869 (Consolboard Inc. v. MacMillan Bloedel (Sask.) Ltd.,  1 S.C.R. 504, 524). That is true too of the duty to disclose an inventor’s best mode. Only explicit language can remove a duty that has been part of Canada’s patent law from inception. As the focus of inventing activity over the last century has moved away from machines to other sectors, subsection 27(3)(c) should be recognized for what it is: the panda’s thumb of Canada’s disclosure provision.
David Vaver is a Professor of Intellectual Property Law at Osgoode Hall Law School and on the Advisory Board of IP Osgoode.