Death of the ‘six year rule’ in Indian patent law jurisprudence

The birth of the rule: In the 1965 case of Manicka Thevar v. Star Ploughs the Madras High Court laid down a rather doubtable proposition of law. In this case the plaintiff had requested the Court to grant it an interim injunction restraining the alleged infringer from infringing on his patent. While deciding the case the Court held that it would not grant an interim injunction in those cases where the patent was a recent one and where its validity had been seriously challenged. The Court proceeded to define a recent patent as one which was not more than 6 years old. It is not too clear why the Court laid down 6 years as the benchmark. The only authority it claimed in support of the ‘6 year rule’ was the English commentary – Terrell on Patents. A noteworthy criticism of this rule has been the fact that it makes no sense to attach a stronger presumption of validity to a patent after 6 years for the mere reason that it has not been challenged for the first 6 years. Such a stance would make it tougher to challenge the patent after the first 6 years. The question of validity of the patent should be dependant only on the facts of the case and not on obscure time factors.
Regardless of the logic or the lack of logic behind the ‘6 year rule’, the fact remains that several judgments, especially Delhi High Court judgments picked up on this rule and applied it in several cases to deny interim injunctions in all those cases of patent infringement where the patent was less than 6 years. Although this 6 years rule has never formed the only basis in law to deny an injunction it was mentioned quite regularly without even pausing to understand or mention the reasons for fixing 6 years as a benchmark.

The possible logic behind the rule: Traditionally even English Courts were reluctant to grant interim injunctions when the patent was relatively new because of the fact that the process to grant a patent was quite complex and more often than not it could be presumed that a patent office would err in the grant of a patent. However this was the situation in England before it introduced post-grant opposition mechanisms. With the introduction of the post-grant opposition mechanism the quality of patents was presumed to have increased since there was now an opportunity to challenge a patent soon as it had been granted. In American Cyanamid Lord Diplock pointed out how the post-grant opposition mechanism had attached to all patents a stronger presumption of validity.

The Delhi High Court adopting the rule: The Delhi High Court however not only borrowed on this rule from Manicka Thevar but also proceeded to hold in the case of N.R.D.C, New Delhi v. The Delhi Cloth and General Mills Co. Ltd. and Ors (1980) that as “a rule of practice that if a patent is a new one, a mere challenge at the Bar would be quite sufficient for a refusal of a temporary injunction”. Amongst other cases this proposition was followed unquestioningly by the Delhi High Court in the Standipick case (2000) and once again in the relatively recent Bilcare (2007) case. It was only in the Roche v. Cipla case (2008) that Justice Bhat of the Delhi High Court finally paused to question the logic of this rule and also express his “bafflement” at this rule. In relevant part he laid down that the 6 year rule “has to be seen as a rule of caution and prudence rather than a rigid, ritualistic formula of mathematical application.”

The death of the rule: Justice Bhat will be happy to know that a couple of judges from the Madras High Court hearing the ‘banana leaf patent’ case shared his ‘bafflement’ at the ‘6 year rule’. The counsel in this case had argued that the ‘6 year’ rule was borrowed by the Manicka Thevar Court from the 1886 RPC 379 – Moss v. Malings case and that the ‘6 year’ rule was fashioned on the basis of the facts of that case which were not relevant to 21st Century India. THe Court seems to have bought this argument because paragraph 66 of the judgment effectively over-ruled the ‘6 year’ rule of Manicka Thevar when it reasoned that the times had changed since the formulation of the ‘six year’ rule and in these days given the rapid advances of science and technology in the competitive market space, any patented technology would fast lose its relevance in the marketplace. Hence it can be concluded that the Court was of the opinion that the first 6 years were of too much significance in today’s marketplace to deny a patentee his rights for the mere reason that somebody challenged it through revocation proceedings. After all an invention maybe obsolete after 6 years. Hopefully with this judgment the Madras High Court has put to rest this ‘6 year’ rule. The question of validity of a patent should remain purely a question of fact and not a question of age of the patent.

Prashant Reddy

T. Prashant Reddy graduated from the National Law School of India University, Bangalore, with a B.A.LLB (Hons.) degree in 2008. He later graduated with a LLM degree (Law, Science & Technology) from the Stanford Law School in 2013. Prashant has worked with law firms in Delhi and in academia in India and Singapore. He is also co-author of the book Create, Copy, Disrupt: India's Intellectual Property Dilemmas (OUP).


  1. J. Sai Deepak...Iyer

    Hey Prashant,
    Thanks for pointing out the overruling of the 6 year rule in the banana leaf case,it completely my mind when i was preparing the draft though i wanted to mention it after reading the judgment. nice post!

    J.Sai Deepak Iyer.

  2. Anonymous

    agree that the six yr rule really comes out from nowhere..but a patent not being challenged is considered a positive in most jurisdictions. Validity is a question of fact..but a patent being long standing and unchallenged has the advantage of the ‘presumption of validity’ argument..which is crucial for interim injunction. Unlike TMs there is no presumption of validity merely by virtue of grant of the patent.


Leave a Reply

Your email address will not be published.