Doctrine of Equivalence

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While adjudicating the infringement suits, courts do follow certain practices and doctrines. These doctrines are regularly used by the law courts, in deciding the infringement suits. In particular, the “doctrine of equivalence” plays an important role in deciding infringement cases.

Doctrine of Equivalence

In general infringement of Patent can be divided into two categories i.e. literal infringement and non-literal infringement. In the case of occurrence of a literal infringement there must be an exact duplication of the claimed patent innovation i.e. when each element claimed is identical to the allegedly infringing device or process. The illustration of the same was done in the case of Polaroid Corp v. Eastman Kodak where it was deemed that directly using the “instant camera technology” of Polaroid by Eastman Kodak is a literal duplication of the said patented invention. Secondly comes the indirect infringement which is guided by the doctrine of Equivalent Patents, in this type of infringement there is a suggestion of certain amount of accidental infringement or mala fide intention. This can be explained by the case of that Ravi Kamal Bali v. Kala Tech and others in which it was said even though the main structure of the body of the claimed product was different from the patented one still the product was held to be infringing since there was no functional or constructional distinction between the two.

What this doctrine says is that where there is no substantial difference between the accused invention and the previously patented invention, the accused invention is equivalent to the patented invention and falls within the purview of the doctrine of equivalents and therefore infringes the patented invention. So basically this doctrine helps the patentee to raise a claim even if the claim of the patented invention is not identically present in the infringing product. The main purpose for the development of this doctrine is to prohibit people from making minor changes to inventions while maintaining the functionality of the said product and denying them access to the advantages of the patentee’s labour and investment.

US and UK Court’s Approach

United States Federal Courts and Courts in United Kingdom, have adopted this doctrine in deciding several patent infringement cases. Courts, while adopting this doctrine often apply function way result test, which examines whether the accused invention performs substantially the same function as the patented invention in substantially same way to obtain substantially the same result. Further courts use to examine the interchangeability between each element of the accused invention and its corresponding element in the patented invention. According to the doctrine, if the accused invention is substantially similar to the patented invention and performs the same functions in the same way that the patented invention performs than the accused invention infringes the patented inventions.

The doctrine of equivalents holds that one cannot avoid infringement by making immaterial or insubstantial changes to the patented invention and take it beyond the scope of the patent claim using the loopholes in the language of the patent claim. The doctrine of equivalent is viewed to be in favor of the inventor or the patent owner in holding that ambiguities and loopholes in the language of the claim and the specification cannot preclude the inventor from holding on to what he has invented and owned. In this connection views of Lord Diplock are very important. In Bristol-Myers Co (Johnson’s) Application speaking for the House of Lords he states that: “In essence what the law of patents is about is stopping people from using things. Where the invention claimed is not a process but a substance irrespective of the means by which it is produced, the rights of the patentees are infringed by anyone who makes or supplies that substance commercially for use by others even though he does not know that it is that substance he is making or supplying.”

Therefore basically the intention of patenting is to stop others from using the invention which has been patented. If anybody who uses the patented invention it does infringe the rights of the patent owner and entitle him to have some legal remedies. Courts in England and US have regularly applied the Doctrine of Equivalents in judging patent infringement disputes quite successfully. Since, the claims in a patent specification are the principal determinants of the scope of the monopoly, claim construction and interpretation of claims are the main issues in an action for infringement. The need for claim construction is necessitated by two conflicting interests

(1) First, is the interest of the inventor not to be destined to lose his right of exclusivity of all or part of his invention by reason of the imperfection of the legal system.

(2) The second is interest of the pubic; to be kept informed of the limits of the inventor’s rights enabling others to formulate and build within the public domain beyond the patentee’s rights.

In England, initially method of strict literal interpretation of the claim was followed, which; say that an act would amount to infringement if it strictly falls within the ambit of literal meaning and scope of the claim. This method had two fold effects; firstly, the claims were needed to be perfectly drafted covering all the variant aspects of the invention. Secondly, it would allow a potential infringer to escape from the liability on the ground of improper or ambiguous draft of claims to the disadvantage of the inventor. This led to the development of another doctrine called “Pith and Marrow Doctrine” in the spear of patent infringement. The notions of the doctrine were quite wide enough to catch the potential infringer. The doctrine brought textual infringement or taking substance from the patented invention within the meaning of infringement. However, this doctrine was considered as a vague doctrine and there felt a need to a fresh approach on the issue of determination of patent infringement.

Also Read  Management and Valuation of Intellectual Property

Following the need for a new approach on interpretation of patent claims in Catnic Components Ltd v Hill & Smith Ltd. House of Lords came with method of “purposive construction” which says that the purpose of the claim drafted by the patent owner to be considered while adjudicating patent infringement suits. It was viewed that specification is a unilateral statement made by the inventor addressing those likely to have a practical interest in the subject matter of his invention. By specification it is informed about what is claimed and what its essential features are. These essential features constitute pith and narrow of the claim. A patent specification and claim should be given purposive construction rather than being purely literal based upon the verbal analysis of what has been understood by the language of the claim. If the persons having practical knowledge in the field to which the invention belongs to would understand the compliance of the words used in the claim as to be intended by the patentee to be essential part of the invention, it renders any variant to fall outside the claimed monopoly. It was opined that the purpose of the language used in the claim has to be understood and given effect, after assessing the same in the eyes of person having practical skill and experience in the field.

Subsequently in Kirin-Amgen Inc v Hoechst Marion Roussel Ltd, the Judge said that if a person skilled in the art understands the specification to have described and demarcated the claimed invention categorically, according to such understanding by the person skilled in the art in the light of the knowledge in the public domain, the claims of the invention and the alleged acts of infringement have to be interpreted and analyzed. If the inventor has used certain language not intentionally and purposefully to form part of the essential features of the claim and the invention, the analysis of such language would fall outside the purview of monopoly. Any alleged act with reference to such language in the claim would not amount to infringement of the patented invention. The intention of purposive construction is to focus on the intention and understanding of the persons skilled in the art with reference to what is claimed and what it encompasses. Once the purpose of the claim and its scope is clear, any alleged acts of infringement could be judged in the light of such purposive scope of the claim.

In USA in Genetech v Welcome Foundation Ltd, the Court of Federal Circuit applied the doctrine of equivalence to decide the infringement of a patent. The invention was a recombinant protein produced through recombinant DNA technology, which activates the protein tissue plasminogen and converts it to plasmin. The defendants were producing a modified protein through recombinant DNA technology with same activating function. The patentees filed infringement suit against the defendants (Welcome Foundation Ltd) alleged to have infringed the patented invention. While testing the defendants method with doctrine of equivalents the court observed that “though the defendants practiced recombinant DNA technology to produce the recombinant protein the same end product as produced by the patent holders, the methods to bind to the fibrin in order to produce the recombinant protein is different” and not equivalent to the method involved in the patent. Eventually it was decided that the practice of the invention of the defendants does not amount to infringement of the patent in the dispute since there is no substantial equivalence. Therefore it can be inferred that as per the doctrine of equivalence when there is no substantial difference between the patented method and the accused method, the practice of the accused method does infringe the patented method. However, if there existed difference between the patented method and the accused method even when the end product is same and the technology is same the practice of the accused method does not amount to infringement of the patented method. The presumption is that if a product is allegedly made out of a patented process it is deemed to be so when there is a substantial likelihood existing that the product was made by the patented process, and when the plaintiff in the suit for infringement was able to determine the actual process involved in producing alleged products. In such circumstances the burden lies on the alleged infringer to prove that the patented process does not make the alleged product.

Further, Regents of University of California v Eli Lilly, illustrates how invalidity or insufficiency of description could be successfully taken as a defense in patent infringement cases. A patent, which suffers from insufficient disclosure, cannot be maintained and no suit can be instituted against infringement of the same.

Indian Approach

In India also the doctrine of equivalents as followed in England and US was closely observed in deciding patent infringement disputes by the courts. The notions of pith and substance and as well purposive construction were also equally observed by the courts. In FH & B Corporation v Unichem Laboratories, a suit for patent infringement under Section 29 of the Patent Act was adjudicated. The invention was pertinent to manufacturing of new urea and salts of those compounds granted a patent under the Indian Patent Act. When the defendants started working on a similar process, the plaintiffs instituted suit for infringement proceedings against the defendants. Defendants counter claimed invalidity of the patent on the grounds of; insufficiency of description, want of monopoly, no novelty and no inventive step. The court felt that the onus of proving the invalidity was on the defendants. However, while looking into the invalidity of the patent on the above grounds, the court observed that patent holder had given as many as 40 examples with reference to the making and working of his invention in the description. It was viewed by the court that following those examples there would no difficulty in practicing the invention. It was viewed that alleged knowledge as to have reflected in the prior art not necessarily make the invention obvious, because practical application of an idea and rough knowledge about the idea or totally different. The court also opined that the patent holder had detailed about the various steps and techniques involved in the making and application of his claimed invention, which are totally new. On these findings the court opined that claims of invalidity of the patent stands rejected and the act of the defendant’s amount to infringement. The plaintiffs were granted injunction stopping the defendants from further continuing with their act constituting infringement and were ordered to deliver up or destruction of all articles made in infringement of the plaintiffs patent. This case is an example for patent infringement proceedings in India where in invalidity of patent was claimed unsuccessfully by the defendants on the basis of doctrines such as doctrine of equivalents and the like.


Hoffmann-La Roche Ltd v Cipla Ltd is regarded as the first Patent Litigation in India post India’s 2005 Product Patent Regime which included public interest and pricing issues in addition to India’s section 3d that prevents ever greening. Roche sued Cipla in 2008 before Delhi High Court claiming that Cipla’s generic product Erlocip violates former’s Indian ‘774 patent claiming “Erlotinib Hydrocloride”. The trial Judge rejected Roche’s appeal to grant interim injunction restraining Cipla from selling generic version of Tarceva on the grounds of public interest and the fact that there was an ongoing patent revocation proceedings against ‘774 patent. Roche’s subsequent appeal to Division Bench also failed when not only did the bench uphold the findings of Trial Judge but also imposed costs on Roche for suppression of material patent information about Roche’s later filed application in India. This was the Patent Application which was actually on Polymorph Form B of Erlotinib Hydrocloride but was rejected in 2008 Roche’s subsequent appeal before the Supreme Court (SC) challenging the order passed by the division bench got dismissed due to the ongoing trial at the Delhi High Court.

Further, in Bajaj Auto Ltd v TVS Motor Co Ltd, the matter involved was the controversy regarding the unauthorized application of the patent of the DTSi technology. The case became very vital regarding the doctrine of pith and marrow also termed as Doctrine of Equivalents. The plaintiffs (Bajaj Auto Ltd), along with the state of Maharashtra alleged the defendants (TVS Motor Company Ltd.) of infringement of the patents of the plaintiffs, which apprehended the invention of the technology of advanced internal combustion engine. The plaintiffs sought remedy of permanent injunction and damages for obstructing the defendants from using the technology prescribed in the patent. The Supreme Court observed that suits relating to the matters of patents, trademarks and copyrights are pending for years and years and litigation is mainly fought between the parties about the temporary injunction. The Supreme Court directed that hearing in the intellectual property matters should proceed on day to day basis and the final judgment should be given normally within four months from the date of the filing of the suit. The Supreme Court further directed to all the courts and tribunals in the country to punctually and faithfully carry out the aforesaid orders.


Despite the fact that the doctrine of equivalent patents has been evolved in foreign jurisdictions for over a century, Indian jurisprudence has yet to articulate a non-ambiguous and clear stance on the same. Though there have been a few instances emphasizing the prevalence of non-literal infringement and addressing the Equivalent doctrine, but the Indian courts have yet to take a firm stance on the doctrine’s application. Since the theory has not been properly and linguistically articulated in the Indian context, there is a lot of discrepancy and misunderstanding among the general population regarding the same. On one side, an innovator must live in continual fear that a third party may sue it for infringement under the theory of equivalent, even though it has attempted and avoided all of the patented items and processes’ actual claims. A victim patentee, on the other hand, may never be sure if going to court would provide him with remedy under the concept of equivalent patents because the doctrine’s presence is extremely subjective and unpredictable. The Equivalent Patents Doctrine was created to shield a patentee against non-literal infringement of their patent. However, it is still upon the courts to decide that how non-literal this infringement can be.