Non-literal Infringement: Clarity or Confusion?

Discussing the Delhi High Court’s recent interpretation of the doctrine of equivalents in  SNPC Machines Private Limited & Ors. v. Mr Vishal Choudhary , we are pleased to bring to you this post by SpicyIP intern Vishno Sudheendra. Vishno is a second year law student at the NLSIU, Bangalore. His previous post can be accessed here .



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Non-literal Infringement: Clarity or Confusion?



By Vishno Sudheendra



The Delhi HC on 5th March 2024 pronounced an order, in SNPC Machines Private Limited & Ors. v. Mr Vishal Choudhary , which discusses a case of non-literal infringement of a patented brick-making machine. The Court, in the context of this order, examines the Doctrine of Equivalents, a doctrine developed in the USA, and the Doctrine of Pith and Marrow, which is a doctrine developed in the UK. I seek to analyse the order and argue that the court by oddly combining both of them has brought about more confusion than clarity.



A Brief Overview of These Doctrines



I seek to provide brief explanations of the concerned doctrines for greater clarity before diving into the case.



Doctrine of Equivalents: This doctrine originates from the US jurisprudence, specifically from the SCOTUS case Graver Tank & Mfg. Co. v. Linde Air Products . It allows a patent holder to claim infringement even if an accused product/process does not literally infringe the language of the patent claims, but instead infringes in a non-literal manner by substituting product/process elements with equivalent elements. (Praharsh discusses the doctrine here ). The scope of the doctrine of equivalents hinges on two factors: the test for equivalence and the legal barriers to equivalents. In the USA, Courts have established five legal tests to restrict the application of the doctrine: the all elements rule, the triple identity test focusing on function, way, and result, the insubstantial differences test, the obviousness test, and the known interchangeability test ( Patodia, Jain and Shukla ).  Amongst the aforementioned tests and limitations, the ‘all elements rule’ and the ‘triple identity test’ are relevant to our discussion since the Court deals only with them.



‘All elements rule’ : The ‘All Elements Rule’ limits the doctrine of equivalents. It mandates that the test for equivalents must be applied to individual elements, not the invention as a whole, to prevent the elimination of any element entirely ( Hilton Davis Chemical Co v. Warner-Jenkinson , Patodia, Jain and Shukla ).



‘Triple identity test’ : It serves as a foundational test for the Doctrine of Equivalents. It states that an infringement is caused by the accused product if it ‘performs substantially the same function in substantially the same way to obtain the same result’ [ Sanitary Refrigerator Co v. Winters ]. This test is applied in conjunction with the ‘all elements rule’



The Doctrine of Pith and Marrow: This Doctrine originated in the UK jurisprudence Clark v. Adie , (paywalled). The principle of ‘pith and marrow’ delineated the extent of patent protection based on the core substance of the invention. Under this doctrine, infringement could be proven if the defendant’s device or method incorporated all the crucial components of the patent ( Mathur ).  



It is to be noted that in the UK, the Catnic Test or the Doctrine of Purposive Construction replaced the Doctrine of Pith and Marrow, in Catnic Components Ltd. v. Hill & Smith Ltd . (paywalled) The Catnic test emphasizes interpreting patent claims purposively to discern the inventor’s intended scope of protection, in contrast to the Doctrine of Pith and Marrow which focuses on the substance of the invention while considering essential elements ( Mehra ). However, post- Actavis v. Eli Lilly ([2017] UKSC 48), the UK Supreme Court seems to have injected the Doctrine of Equivalents ( Cordery ).



So what is the difference between The Doctrine of Equivalents and The Doctrine of Pith and Marrow?



The Doctrine of Equivalents would apply even if both essential and unessential elements are substituted with their equivalents in the infringing product/process. However, for the application of the Doctrine of Pith and Marrow all essential elements have to be the same in the infringing product/process while only unessential elements may be substituted with its equivalents ( Mathur ). Therefore, the Doctrine of Equivalents by allowing for equivalents for both essential and unessential elements, via the triple identity test provides a much broader scope for non-literal infringement vis-a-vis the Doctrine of Pith and Marrow.



The Order



The plaintiffs, SNPC Private Limited and others, filed an application seeking a permanent injunction against the defendant, Mr Vishal Choudhary, from using, making, manufacturing, offering for sale or selling or importing the impugned brick-making machines. It was alleged that the defendant was manufacturing and selling brick-making machines which were similar to the plaintiffs’ patented brick-making machines. The plaintiffs alleged non-literal infringement based on the doctrine of pith and marrow and the doctrine of equivalents. The defendants contended that since the allegedly infringing product lacks a cabin, steering, steered front wheels and motorization of rear wheels, the  ‘all elements rule’ must be applied whereby the product must contain every element of claim of the suit patent and if even a single element is missing from the allegedly infringing product, it would not amount to infringement.



The Court observed that the ‘all elements rule’ has to be used in a qualified manner. An infringer may, if the ‘all elements rule’ is not qualified, deploy minor variations in a product which has multiple elements and contend that the product does not infringe the patented product even though it performs the same function in substantially the same way to obtain the same result. The Court emphasised that the essential idea for seeking a patent is for the commercial exploitation of the same. It was further observed that the triple identity test becomes critical in the examination of infringement because the primary object of the infringer is to produce a product which competes with the plaintiffs’ product. If an infringer’s product undermines the patentee’s product, even with slight modifications, it undermines the fundamental goal of the patent. Thus the Court held that it is necessary to apply both the pith and marrow test and the triple identity test to assess potential infringement. Based on the aforementioned analysis, the Court dismissed the defendant’s submission while recording that “ the all-elements rule cannot be adopted to the exclusion of the pith and marrow rule .”



The Court observed that the pith and marrow of the plaintiffs’ invention is to provide for brick assembly with mobility. After considering the aforementioned principles, the Court granted the injunction, while holding that the lack of elements in the defendant’s machine is not essential given the product also provides for brick assembly with mobility.



Analysis



The legal landscape regarding non-literal infringement in India has no clarity i.e., Courts have applied either the doctrine of pith and marrow or the doctrine of equivalents, and there existed no judgment which prioritized one doctrine over another (To read more refer to this ). In the given case the Court has given significant importance towards the doctrine of pith and marrow and further also held the same to be prioritized over the ‘all elements rule’ which is part of the doctrine of equivalents. The prioritization of the Doctrine of Pith and Marrow is desirable in the Indian context, as commented by Prof. Sarnoff on SpicyIP earlier ( here ) because the Doctrine is an import from the UK jurisprudence to which Indian jurisprudence is much closer compared to the US jurisprudence. Further, the Doctrine of Equivalents extends the patent protection beyond the scope of the interpreted language allowing for the substitution of essential elements if the substituted elements pass the triple identity test, whereas the Doctrine of Pith and Marrow requires the presence of all essential elements, and only unessential elements may be substituted by its equivalents.



However, this prioritization of the Doctrine of Pith and Marrow is followed by the Court’s assertion that the Doctrine “ought to be used alongside the triple identity test”, a test used to determine equivalence under the Doctrine of Equivalents. So on one hand, the UK’s Doctrine of Pith and Marrow seeks to consider the substance of the invention and ignore non-essential variations, and on the other hand, the USA’s Doctrine of Equivalents considers the equivalence of elements of the product via the triple identity test. Coupling the triple identity test with the Doctrine of Pith and Marrow creates more confusion than providing clarity in the given legal landscape. 



The prioritization of the substance of the invention via the Doctrine of Pith and Marrow over the ‘all elements rule’ and the doctrine coupled with the triple identity test leads to substantial expansion of scope for claiming non-literal infringement, under the said doctrine. This expansion is caused because of the incorporation of the triple identity test which would also allow for the equivalence of both essential and unessential elements, while the Doctrine of Pith and Marrow originally allowed only for equivalence of unessential elements.



The aforementioned expansion by combining the two doctrines, coupled with the exclusion of the ‘all elements rule’ should be applied judiciously as a precedent while considering the decision of the Canadian Supreme Court in the case of Free World Trust v. Electro Sante Inc . , where it was emphasised that “the ingenuity of the patent lies not in the identification of a desirable result but in teaching one particular means to achieve it. The claims cannot be stretched to allow the patentee to monopolize anything that achieves the desirable result.”  



Conclusion



The order highlights the court’s decision to prioritize the doctrine of pith and marrow over the ‘all-elements rule’ under the doctrine of equivalents. While emphasizing the importance of considering the substance of the invention, the court’s coupling of the pith and marrow doctrine with the triple identity test, typically associated with the Doctrine of Equivalents, introduces complexity and potential confusion into the legal landscape. This approach expands the scope for claiming non-literal infringement by giving precedence to the overall substance of the invention over the analysis of specific elements and claims. However, the expansion should be viewed with caution given that a patent does not (i.e., should not) provide a license to monopolize anything that achieves the desirable result.