A patent is a form of intellectual property that gives the right to an inventor who has created something new, useful and non-obvious. Patent rights give owners the privilege to prevent another from taking advantage of their invention and allows them a fair return on their work and investment. A patent work always requires to be defined in "full, clear, and, concise" terms.

Sometimes, copying of the patent might not be a literal imitation, but may provide the same effect. If such copying is allowed, the purpose of granting the patent rights to the inventor will be meaningless. It will become easy for any person to imitate the patent by making minor changes and enjoy returns larger than those accruing to the original inventor. To counter such behavior, Doctrine of Equivalents was introduced. It was decided by court that infringement may occur even though the literal language of the claims was avoided.

Doctrine of Equivalent in Patent Infringement

The violation of the exclusive rights of the patent holder leads to patent infringement. Any person is liable to infringement if he exercises the exclusive rights of the patent holder without the patent owner's authorization or license. Section 104 to 114 of the Indian Patent Act 1970 provide guidelines related to patent infringement. Two kinds of patent infringement are defined - Direct Patent Infringement and Indirect Patent Infringement (Doctrine of Equivalents).

Direct Infringement is the most common type which occurs when a product that is close to any patented product or invention is used commercially or marketed without permission from the owner of the patented product or invention. Patent infringement generally falls into two categories - literal infringement and infringement under the doctrine of equivalents. When each element claimed is identical to the allegedly infringing device or process, it is literal infringement.

A claim may be infringed under the doctrine of equivalents if it falls under the "triple test", i.e. equivalence holds when the substituted elements perform substantially the same function in substantially the same way to obtain the same result.1

What is an "All Elements" test?

The "All Elements", test says that the doctrine of equivalents must be applied to all the individual elements of the claims and not the claimed invention as a whole. It is necessary to prove that every element of the patented invention, or its substantial equivalent, is present in the accused product or process.

The elements of the patented invention must have substantial equivalents in the new invention. This means that they must meet the rules of the triple identity test. Equivalency should only be considered after a claim has been filed. It should not occur when an invention is patented.2

The theory related to Doctrine of Equivalents is based on the triple identity test, i.e. if two devices do the same work in substantially the same manner, and attain substantially the same output, they are considered to be same, even though they vary in the name, form, or shape.

Few factors related to substantiality are:

  • Whether persons skilled in the art actually know of the equivalence of the claimed and accused inventions.
  • Whether persons skilled in the art could have known of the equivalence.
  • Whether he had intended to copy, or, rather intended to design around, unintentionally arrived at the same result.

Under the doctrine of equivalents, a patent claim may be found to infringe if there is "equivalence" between the elements of the accused product or process and the claimed elements of the patented invention, even if that does not literally infringe upon the express terms of patent claims.3

Position in India: Doctrine of Equivalents

A case of Ravi Kamal Bali vs Kala Tech and Ors brought forward the doctrine in India. The suer, instituted an infringement suit seeking an interim injunction preventing Kala Tech, the defendant, from making, selling or distributing tamper proof locks/seals as it would be the infringement of his patent. He argued that Kala Tech's perform the same work, in substantially the same manner and gives the same output thereby contributing to the infringement. He asked the court to apply Doctrine of Equivalents, while considering the question of infringement of patents. Although the interim injunction was not granted, the importance of the case lies in that, it was the first case where the doctrine of equivalents was discussed in India.

In other cases like, the case of Bishwanath Prasad Radhey Shyam vs Hindustan Metal Industries, it was observed by the Supreme Court that the proper way to interpret any specification is to first read the description of the invention and then see what is claimed in the invention, as the patentee cannot claim more than he desires to patent.

The application of the doctrine of equivalents in the matters of infringement is a big step for the Indian Judiciary, the judgment has also received severe criticism as the High court has several times failed to take into account the legal bars to the application of the doctrine as recognized by the US Judiciary in several matters. 4


Despite the doctrine having been around for almost 150 years, a sorted, linguistic framework is yet to evolve. It creates ambiguity and difficulty in application. If a member of public creates an invention, even after looking into the literal scope of the claims and falling outside of it, might later find to have infringed the same patent under the doctrine of equivalents. Finding of equivalence is a determination of fact, proof can be made in any form through testimony of experts skilled in the field or an authoritative document on the subject. With reference to India, it can be concluded that so far there have been very few cases dealing with patent claim infringement. In spite of that, the pace at which technological advancement is taking place, the Indian judiciary is likely to face similar cases in near future. India can formulate its own theory based on sound techno-legal reasoning in striking a balance between conflicting interests of protection and innovation.5


1 http://www.legalservicesindia.com/article/2532/Infringement-ofPatents.html

2 https://www.legaladvantage.net/blog/doctrine-of-equivalents/

3 http://docs.manupatra.in/newsline/articles/Upload/61DFD921-5C67- 4C34-9C6F-FC946AB34821.pdf

4 http://www.legalserviceindia.com/legal/article-4-doctrine-ofequivalents-and-prior-history-estoppel.html

5 http://docs.manupatra.in/newsline/articles/Upload/61DFD921-5C67- 4C34-9C6F-FC946AB34821.pdf

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