In a landmark judgment, the Delhi High Court noted that “A monopoly of the patent is the reward of the inventor”.
While adjudicating patent infringement matters, Indian Courts have appreciated the huge investment of time, and resources in the form of research and development that inventions demand. Indian Courts have also noted and commented on the critical requirement for protection of patents from imitations, whether or not such imitations are literal.
In certain scenarios, an imitation of a patent might not be an ‘literal imitation’ in the sense that it may fail to disclose each and every element of the claims of the patent invention. However, such an imitation may provide the same effect. If such imitations are permitted, the entire purpose of granting the ‘exclusive right’ of patent to the inventor would be defeated.
Thus, in order to discourage such practice, the Doctrine of Equivalents was evolved. Infringement under Doctrine of Equivalents can be understood as an infringement of a patent claim even if it is not literally infringed if the allegedly infringing device or process "performs substantially the same function in substantially the same way to achieve the same result" as the patented invention.
Broadly, patent infringement analysis comprises of two steps, namely, literal infringement analysis and non-literal infringement analysis (also referred to as infringement as per the doctrine of equivalents). In literal infringement analysis, a claim is analyzed along with the alleged infringing product or process in order to ascertain the presence of all elements of the claim in the alleged product or process using literal language of the claim to establish the scope of the claim. If the alleged infringing product or process encompasses all the elements of the patent claim, when the scope of the claim is construed by the literal language of the claim, such claim is said to be literally infringed by the respective infringing product or process.
However, where literal infringement cannot be established following the above test, the scope of protection conferred by the claim is extended beyond the literal language of the claim. Non-literal infringement of patents have been addressed and dealt with extensively by the US judiciary.
Though on relatively fewer occasions, the Indian courts too have had to deal with matters involving non-literal infringement. At the outset, it can be observed that the Indian judiciary notably favors purposive construction of claims, thereby extending the scope of claims beyond the literal language of the claims in such matters.
In the matter of Raj Prakash v. Mangat Ram Chowdhry and Ors, the Delhi High Court for the very first time discussed and addressed the concept of non-literal infringement. Though the Hon’ble Court did not use the phrase ‘Doctrine of Equivalents’, while quoting words of Lord Denning in Beecham Group Limited v. Bristol Laboratories Ltd. & Anr. stipulated the following :
“...there is a further point. A person is guilty of infringement if he makes what is in substance the equivalent of the patented article. He cannot get out of it by some trifling or unessential variation....”
Further, the Court held that
“It is the pith and marrow of the invention claimed that has to be looked into and not get bogged down or involved in the detailed specifications and claims made by the parties who claim to be patentee or alleged violators.”
Purposive construction of claims was also accepted by the Madras High Court in TVS Motor Company Limited Vs. Bajaj Auto Limited, wherein the Hon’ble High Court held the following:
“In construing an allegation of infringement, what is to be seen is whether the alleged infringement has taken the substance of the invention ignoring the fact as to omission of certain parts or addition of certain parts.”
Further, in Ravi Kamal Bali v. Kala Tech, wherein the Plaintiff had sought for an injunction restraining the Defendants from making of, using, selling or distributing ‘tamper proof locks/ seals’ that fell within the scope of Plaintiff’s invention, Justice Vazifdar applied the Doctrine of Equivalents. He opined that the two products, evidently had the same usage/purpose, nature of material and also worked on the same principle. The Court further opined that the difference of main structure of body makes no difference and it does not imply a new invention. In conclusion, the Court was of the view that the alleged infringing product of the Defendant did infringe the patent invention of the Plaintiff. The primary reason was that there were no substantial differences between the products as the constructional and functional aspect of the product had remained the same.
Though, the application of the doctrine in matters of infringement is a big step for the Indian judiciary, the judgment has also received severe criticism as the Hon’ble High Court failed to take into account the legal bars to the application of the doctrine as recognized by the US Judiciary in several matters. The legal bars to the application of the doctrine ensure that the doctrine does not conflict with the fundamental principle that claims define the limits of patent protection.
Thus, it is evident that the Indian courts do not limit the scope of protection conferred by a claim to the literal language of the claim. Further, in light of the above judgments, it can be noted that the “pith and marrow” or the “substance” of the invention has to be looked into while ascertaining and defining the scope of a claimed invention.
Conclusively, it has been observed that the current position of the Indian judiciary is in favor of patent holders with respect to their right to enforce the protection of their patents against those against infringers attempting to avoid liability by merely playing semantic games or making superficial changes. However, it is imperative for Applicants to ensure that the claims are crafted carefully to capture the “substance” or “crux” of the invention, and should avoid including non-essential elements in the claim. On the other hand, those attempting to work around a patent claim without infringing such claim should not rely on minor superficial modifications to a claimed product or process, which may be inferred as not going beyond the “substance” of the patent claim.
 AIR 1978 Del 1
 1967 (16) RPC 406
 (2008) ILLJ 726 Mad, MIPR 2008 (1) 217, 2008 (36) PTC 417 Mad
 3 2008 (110) Bom L.R. 2167
 Charles Griener Co. Inc v. Mari-med Mfg., 22 USPQ 2d 1526