Doctorine of Equivalance and Prior History Estoppel

“Owning the IP is like owning land: You need to keep investing in it again and again to get a payoff; you can’t simply sit back and collect rent.” ~  Esther Dyson


Any original creation that is created by human intellect artistic literary technical scientific creation is called an intellectual property; any legal rights that are given by the state to the inventor of the invention for the creator of the creation in order to protect it for a certain period of time is called intellectual property rights. These rights are given exclusively to the inventor /creator to utilize invention/ creation for a brief future

Patent is a form of intellectual property rights which is granted for various kinds of invention which fulfill the patent-ability criteria. It is granted by the government to be inventor for a limited period of future

This in turn shows that the inventor can fully extract its invention because creating or inventing anything any invention takes a lot of investment. Patenting it allows them to get a fair return on their investment.


Claims for any instruments of an intellectual property is very hard for the legal instruments IF the inventions or the creation sometimes you invent or create can be very complicated for example, there are many headlines in the newspapers globally that some company has won over another company example, Novartis’s patent is being challenged by DRL in US Court, Nokia won over InterDigital over a dispute which was regarding a patent. Doctrine of equivalence is applicable in a situation where there is no immediate infringement but there may be an infringement over the structure or performance of a function that is a vital part of the claim.

It was by the judicial efforts of the US Supreme Court in the case of win. v Den[1]. where the supreme court of the United States said “The value of a patent will be none if the defendant changed the invention in a simple manner and claimed over it.” There is a restriction by the courts so that the competitors be restricted in making any insignificant changes or modification of the invention that is claimed, the house of justice has struggled to maintain a balance in computing policies of the people and protecting reasonable certainty from them.

This supposition is based on that there are two inventions that are very similar in their functions and, similarly they produce the same outcome even though they may have a different name, size, order and state.

The difference between the creations or inventions and the accused invention must be insignificant otherwise this theory is not applicable.

There are certain factors relating to test whether the substantiality is there or not:

  1.  People with the talent in their art actually have the knowledge of the equivalence of both the devices.
  2. If the people with the talent are informed about the presence of the equivalence or not.
  3. If they had the intention to mimic or rather any malicious intent to find their way around the product to produce a similar outcome.


It is submitted that we have a poorly analysed, sloganistic environment of patent case laws, which are rather poorly and thoughtlessly analysed.[2]

This doctrine was first seen in India in the case of R.K. Bali versus KT & ors.[3] , Most important part of this case is this,  which was the first case in the country that discussed the doctrine of equivalence, here R.K. Bali  has find a suit in the court seeking an interim injunction over the Defendant.

In the dispute of B.P.R. Shyam v H.M.I.[4], the Hon’ble Supreme Court Pointed out in Arnold v bradbury[5], in order to come to a conclusion we must read the description of the invention and then their mind to know what the claim is rather than opposite which is reading the description regarding invention, it should be accorded that the claim of the plaintiff should be just.


This doctrine of prosecution history estoppel prevents the plaintiff of a case of patent infringement from pertaining the same coverage of the subject matter from the previous doctrine that had been seized when the proceedings of the patent application were held.

 The apex court in the United States of America, in the suit of F.C. V S.K.K. Kabushiki Co[6].meet the application of this doctor and permanent.

Looking at the following summarized points we can see what was the decision of the Hon’ble court in this case.

  1. Any number of the amendments that are narrowing and are made in accordance to the needs of statute may lead to it.
  2. If there are any amendments which are narrowing and unexplained, amendment will be presupposed, that is made in accordance to the needs of the statue.
  3. The scope of attraction between the claim is presupposed to have been surrendered before and after the amendment
  4.  To show whether the same question of equivalence was surrendered or not is the burden of the plaintiff.


This doctrine of equivalents has been around for 150 years. Though it has been around for over a century a precise and a settled Framework is yet to be devised.  The absence of a settled framework leads to difficulty in applying the doctrine and it creates vagueness.  It will interfere with the functions of the public when it is applied broadly.

It usual to see people who really want to develop an invention around another invention, without any malice and if they find some positive results, they will be held guilty due to this concept. Due to this doctrine and there is a lack of innovation because of the justification and the fare arguments that lack in their support and also if anyone innovate around  anything this will lead to  high social costs conflicting with intents of the defendant.

 From the perspective of India it can be summarized, the number of cases in India is comparatively low with the claim of patent infringement but it can also be said that due to the speed of the innovations in the technological department, the Indian judiciary should be prepared to deal with subsequent cases in the coming time.  Our country can also computer its own position over this supposition for the legal reasons by harmonizing between computing policies of the people and protecting reasonable certainty from them.


Though with downsides doctrine but the part where the doctrine talks for of the innovators, can’t be overlooked. The American courts have given a good example how to apply this doctrine by restricting or limitations over it. If in the same this doctrine is enumerated in the laws of India it would be highly beneficial to the people as the cases regarding this will rise in the future.



[1] 56 U.S. 330 (1854)

[2]  6 As can be seen in the case of Lintech Electronics (P) Ltd and Anr v Marvel Engineering Co and Anr, 1995 (35) DRJ 11, wherein Delhi High Court confused patents with copyright and instead of analysing the scientific principles of the Acoustic Steam Leak Detection System machine, and interpreting the claim it relied on copyright in the drawings and designs relating to the system and then decided the case. I believe there is lack on willingness on the part of Judges to understand the Scientific principles and then decide the case; Moreover, there are very less patent filed and granted in India so consequently, there is lack of patent litigation in India.

[3]  2008(110)Bom LR 2167

[4]  AIR 1982 SC 1444.

[5] (1871) 6 Ch A 706.

[6]  122 S. Ct. 1831, 62 U.S.P.Q.2d 1705.

Author: Kashish Goel,
Delhi Metropolitan Education, GGSIPU 4th Year

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