“Purposive Construction”: Has certainty been compromised?

Heather Hui-Litwin is a J.D. candidate at Osgoode Hall and is taking the Patent Law course.

In patent litigation, claim construction is an extremely important aspect in the analysis of a patent. Findings of infringement and validity ultimately depends on the construction. The leading cases on claim construction is Free World Trust v. Electrosante (2000 SCC 66, [2000] 2 S.C.R. 1024)  and Whirlpool Corp. v. Camco Inc., (2000 SCC 67, [2000] 2 S.C.R. 1067), which upheld the doctrine of “purposive construction”. 

In Free World Trust, the court enumerated the proper steps in construing claims, which include, amongst other things, interpreting the patent through the eyes of an ordinary person skilled in the art, prior to any validity and infringement analysis, with regard to the intent of the inventor. Furthermore, in Whirlpool, the court endorsed what Dickson J. said in Consolboard Inc. v. MacMillan Bloedel ((Sask.) Ltd., [1981] 1 S.C.R. 504) that “We must look to the whole of the disclosure and the claims to ascertain the nature of the invention and methods of its performance” (Whirlpool, para. 49)

With the arrival of purposive construction, one wonders if the primacy of claims still hold, as the court held that one must look to the disclosure for meaning of the claims.  This raises some anxiety in patent analysis.  One used to be able to discern the boundaries of what is claimed in the claims themselves. With purposive construction this does not hold any more!  The court tells us to read the patent as a whole, rather than look solely to the claims, to determine what is claimed.  Furthermore, this holistic approach would appear to give the patentee flexibility in arguing the exact scope of his claims.  It has been argued that claims themselves ought be unambiguous.  They should give certainty to the public just what is fenced off.  To allow a patentee to rely also on the disclosure is to introduce uncertainty into the claims, which would allow the patentee to claim more than what was in the claims themselves.  Are these concerns justified?

When I first read Whirlpool, I was not sure if I liked this new way of construing claims. The case turned on the construction of the word “vanes”.  When I read the claim in question, I thought it was clear: the device included “vanes”, which in my mind, not being a person skilled in the art of washing machine manufacture, meant any kind of vane.  The expert for the patentee actually testified that at the date of the patent, the only kind of vane contemplated was rigid.  Hence, the construction accepted by the court of the word vane by a person skilled in the art is a rigid vane.   That, to me, almost seems to be adding in words to the claim itself! Really, when the patentee meant rigid vane, why did they not say so? Surely it is the duty of the patentee to be crystal clear about what it is they are claiming. They should not be allowed to broaden or narrow the claims as they please by being allowed to refer back to the disclosure for further definition of their claims.

Even so, I believe this approach makes more sense than a literal or dictionary approach to claim construction, where the claims themselves are dissected with merciless scrutiny,  without context to the patent disclosure.  What the court is trying to say, I believe, is that it only makes sense to read any patent as a whole.  The English language has inherent weaknesses, such as words that have multiple meanings. (Even the word “construction” has multiple meanings, and of course, in this blog, we are not talking about building houses!) Occasionally the grammar in a claim raises difficulties in interpreting the claims. It only makes sense to read the patent as a whole.

I do not believe it is the court’s intention to give the public extra burden in having to read the whole patent.  Nor is it the court’s intention to give unfair flexibility to the patentee in allowing them to claim beyond what is noted in their claims by relying on the disclosure.  Rather, the approach is to ensure a fair reading of the patentee’s invention and what he is claiming.  An unfair expansion of what is in the claims would be where the claim actually read “rigid vane” explicitly, and yet, the patentee argues that because the disclosure included all shapes and sizes and flexiblities of the vanes, that the claim must be read to include these elements.  Binnie J. noted this would not be permitted in FWT (patentee’s own mistake).

The advantage of the purposive approach was clearly demonstrated in a more recent case of Pfizer Canada Inc. v Canada (Minister of Health) (2005 FC 1725). There, the claim was written in such a way as to introduce ambiguity.:

1.     An injectable, ready-to-use, sterile, pyrogen-free, anthracycline glycoside solution which consists essentially of a physiologically acceptable salt of an anthracycline glycoside dissolved in a physiologically acceptable aqueous solvent therefore at an anthracycline glycoside concentration of from 0.1 to 50 mg/ml, which has not been reconstituted from a lyophilizate and the pH of which has been adjusted to from 2.5 to 5.0 solely with a physiologically acceptable acid.

Here, there is issue in whether the phrase “which has not been reconstituted from a lyophilizate” refer to solution or the active ingredient.  Now, one can see right away that this is a grammatical inquiry.  Clearly, the infringing party is engaged in analyzing the actual claim itself in every detail.  Justice Hughes notes that this is just the kind of analysis that the court has warned us not to apply.  If one had read the whole patent, and asked a person in that field about the active ingredient, one would understand the background to this invention: that is, the patentee has invented a safer way of providing the delivery of the drug, which is highly poisonous, and had always required extremely delicate handling by nurses.  The lyophilized active ingredient had always been around, therefore, it makes no sense for the claim to be speaking about the lyophilization to the active ingredient itself.  Imagine if the claim was found invalid for ambiguity, which would allow infringers free access to the invention. It is unfair to the inventor, who disclosed to the world in clear terms the details of his invention, only to be deprived of the monopoly of his invention, solely on the basis of technicality of bad grammar of his claim.

  1. I do not believe the courts are allowing patentees to rely on the disclosure without being cognizant of the risk of uncertainty and of allowing the patentee to claim more than what was in the claims themselves. Two recent decisions are helpful in understanding the court’s perspective on purposive claim construction and its risks:

    Kelen J. in Pfizer Canada Inc. v. Novopharm Ltd. (2009 FC 638) iterated that when “construing the claims for the purposes of considering the validity of the patent, the court must look primarily to the claims” and that “the Court may resort to the specification only in limited circumstances.” (2009 FC 638 at para. 38) Indeed, the “claims alone define the statutory monopoly.” (Ibid.) Consultation with the rest of the patent specification is permitted only for the purpose of understanding terms used in the claims themselves, and is certainly “unnecessary where the words [of the claims] are plain and unambiguous.” (Ibid.) Further, the court considers it improper to use other parts of the patent (e.g., such as the abstract and additional specifications) to vary the scope or ambit of the claims. Kelen J. continued: “This does not mean that claims are never to be construed in light of the rest of the specification but it means that the resort is limited to assisting in comprehending the meaning in which words or expressions contained in the claims are used.” (Ibid.)

    Justice von Finckenstein, in Pfizer Canada Inc. v. Canada (Minister of Health) (2006 FC 1471, 54 C.P.R. (4th) 279) quoted at para. 34 Binnie J. of the Supreme Court of Canada in Whirlpool (at paras. 52 and 45 of Whirlpool) in emphasizing that even though the Court must consider the entire specification of the patent, critical to proper claim construction is the job of extracting the essential pith and substance of the claims, without improperly enlarging the scope of those claims.

  2. Introduction:

    The purposive construction is encouraging as it will, as indicated above by Ms. Hui-Litwin, help eradicate grammatical errors from leading to injustices involving patent claims; all of which is made possible by the legally fictitious ‘skilled reader’.

    Defining The Scope – Not So Easy

    Judicial interpretation plays a significant role in law, and this is no less true in the area of patents. At times we need judicial intervention to properly set out the fenced off area where monopoly rights are granted. One would think that this function of the court would not be needed since in order for a patent to be granted it must give “adequate description of the invention with sufficiently complete and accurate details as will enable a workman skilled in the art to which the invention relates, to construct or use that invention” [R.T. Hughes and J.H. Woodley, Hughes and Woodley on Patents, (Markham: Buttersworth, 1984)]. Nevertheless, the increasing complexity of patents creates challenges to understanding the boundaries of an invention. Given these difficulties courts in Free World Trust c. Électro Santé Inc stated that a claim construction “raises important questions about the scope and ambit of a patent owner’s monopoly” [[2000] 2 S.C.R. 1024, para 3].

    In Free World Justice Binnie correctly recognized the overall tension that “too much elasticity in the interpretation of the scope of the claims creates uncertainty and stifles competition. Too little protection robs inventors of the benefit they were promised in exchange for making a full and complete disclosure of the fruits of their ingenuity” [[2000] 2 S.C.R. 1024, para 3].

    The Skilled Reader and Being Purposive:

    R. Gold and K. Durell indicate that the “skilled reader is employed as a purposive construction tool through which courts attempt to correctly determine the boundaries that dictate the scope of a patent.” [Gold, Richard E. and Karen Lynne Durell. “Innovating the Skilled Reader: Tailoring Patent Law to New Technologies” Intellectual Property Journal 19 189 [Gold and Durell]] Traditionally, these skilled readers did nothing more than contribute technical definitions, and left the court with no “context to understand the potential uses of an invention” [Gold and Durell].

    In the English case of Catnic Components Ltd. v. Hill & Smith Ltd the courts asked the operative question of how should they read patent claims? Canadian courts, after adopting aspects of the English decision, have determined that the skilled readers “have assumed the mantle of the reasonable person able to […] determine what is necessary to constitute the subject matter of the patent” [Gold and Durell]. By using this skilled reader the courts are able to take a contextual approach, but limit the materials to be relied upon. As such, the construction of a claim will only involve tools found within the “four corners of the specification” [Whirlpool Corp. v. Camco Inc [2000] 2 S.C.R. 1067, para. 49(f)].

    There will always be the concern that the court will misconstrue the qualities of the skilled reader, but these chances of error lay in all forms of law. Patent law cannot be denied a vessel, which helps the court balance public interest and rights of the patentee.

    Durell and Gold indicate that by “endowing the skilled reader with a mixture of technical, common and legal knowledge, the court has placed the skilled reader at the heart of the claims interpretation” [Gold and Durell]. The skilled reader will be able to account for context of a claim and therefore ensure that it is not cast to narrowly, as to harm the patent holder; or too broadly, so as to be a public nuisance.


    Using the purposive approach via the skilled reader allows an evolution of patents’ version of the reasonable person; there is “no one better placed than a skilled reader to truly understand the implication of a patent and to be able to assess its scope” [Gold and Durell].

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