Explaining the Delhi High Court judgement in Duraline v Jain Irrigation, Srishti Gaur highlights how it stands out for its findings on design infringement, but falls short on the obviousness analysis of the suit patent. Srishti is a third-year student at National Law University, Delhi. Her previous post can be accessed here.
Dura-Line v. Jain Irrigation: Where the Design’s Test Holds Water but TSM Leaks
By Srishti Gaur
On 19th May, 2025, in Dura-Line India Pvt Ltd v Jain Irrigation Systems Ltd., the Delhi High Court delivered a once-in-a-blue-moon full-trial judgement – the one that walked the tightrope between patents and designs law. After more than a decade of litigation (the suit was instituted in 2013), the Court upheld the validity of the Suit Patent of Dura-Line and dismissed Dura-Line’s allegation of design infringement against Jain Irrigation. Though Dura-Line’s patent expired in July 2023, the Court held that Dura-Line is entitled to relief for past infringement.
This decision holds within itself a tale of contrasts that while the Court adopted a restrictive reading of obviousness of patent on one hand, the Court’s approach to design infringement has been well-balanced. It stood out particularly for its clarity and sound reasoning, especially in navigating the boundaries between the often-confused boundaries between patent and design law.
Why the Dispute?
At the heart of the contestation was the Dura-Line’s patented invention that comprised of a non-metallic pipe on whose outer surface a tracer cable is co-extruded (i.e. simultaneously layered during the manufacturing process) and encased in a suitable polymer material which aids in traceability and detection of leakages, along with its registered design, granted in respect to the “surface pattern” of the pipe.
The Defendant, Jain Irrigation Systems, supplied for a tender, floated for the Omkareshwar Lift Irrigation Scheme, which called for high-density polyethylene pipes (HDPE), having an underground detectability feature, specifically with a co-extruded wire along the length of the pipe. For this tender, Dura-Line was also approached on 25th November 2011 to submit a proposal, however, later, on 11th December 2012, it discovered that Jain Irrigations have already delivered pipes – a revelation that led to the filing of this suit and what followed was a 12-year-long legal saga with its own set of intriguing findings. The post will first look into the DHC’s finding into the design infringement and what sets it apart from the usual set of cases, and subsequently, it will unpack the Court’s obviousness analysis on patent validity.
The DHC’s Departure from Summary Design Inquiries
Eashan Ghosh in his book ‘The Finished Article: Essays on Indian Designs Law’ underscored that in recent times, the courts have titled towards a cursory inquiry into cases of design infringement. While such “cursory inquiries” are acceptable in ex parte cases or where the plaintiff failed to make a prima facie case of infringement, the summary approach adopted by courts otherwise, neglecting the nuanced test of infringement (will be detailed later), has been concerning (pg. 117). He further adds that the Delhi High Court has been at the forefront of implementing such an approach into practice.
In deploying a summary approach, the courts have overridden factual considerations and instead of making a case-based examination, they have mechanically considered infringement inquiries. In addition to it, the entire design infringement inquiry has been reduced to shortcut steps wherein they barely peruse the rival designs, making a general assessment than using the specific eye-test (a standard which is explained later in the section).
However, this DHC case stands on the other side of this progressive decay of substantive infringement inquiries. The Court decided against Dura-Line on its claim of design infringement on two major accounts: first, the registered design falls outside the permissible scope of design protection, and second, even if compared visually, the two designs are not deceptively similar to each other.
The Court noted that the Dura-Line has a registered design with respect to the ‘surface pattern’ of the pipe, which, as per the witness’ explanation, includes polymer-based pipe and polymer-encased co-extruded tracer wire (para 151). Now, as held by the Supreme Court in Cryogas Equipment Private Limited v Inox India Limited and Others, functional features are not a part of design protection. To elaborate further, features dictated by their functional or technical necessity do not fall within the scope of design registration, as said under Section 2(d) of the Designs Act, 2000 – what matters is the overall aesthetics of the product. The Court rightly pointed out that this design registration is not based on visual appeal or ornamentation rather on functional and constructional features which is contrary to the ambit of the Designs Act. The protection of technical aspects falls in line with patent protection than one being of designs (para 152).
The Court used the eye-test to evaluate similarities between the designs of the two parties. In Castrol India Ltd. v Tide Water Oil Co. Ltd. (1994), the Calcutta High Court elaborated the eye-test – in a case of design infringement, similarity in overall visual impression of the alleged infringing design and registered design is considered from the standpoint of an average consumer and it is not identicalness at a technical or a part-by-part manner which is sought out. At last, Castrol laid a four-step inquiry – in a nutshell, first, the court need not look into every resemblance but focus on the article in totality. Second, it is to be assessed whether the design is an essential part of the originality and is reproduced by the defendant or not. Next, the infringement must be tested solely by the eye-test. Last, in judging the article solely by the eye, the courts have to look whether the defendant’s version is an obvious or a fraudulent imitation.
While the Court did not demarcate its assessment into these steps, it abided by the principles laid out in Castrol. Following the precedent, the Court reached the conclusion that when viewed from the viewpoint of an average consumer, there exists no compelling similarity between the two designs. When viewed in totality, Jain Irrigation’s product has a broader contour and different surface structure, which is distinct from Dura-Line’s “surface-mounted linear formation”. Moreover, incorporation of a tracer feature accounts for a functional inclusion and does not make a case for infringement. Finally, the Court found no evidence of deliberate copying or that of intent to deceive as the defendant had no access to the design registration or tailored their products in a fashion which suggests mala fide (para 154).
That said, while the Court’s design analysis was sound and based on precedents, certain aspects in the Court’s patent infringement assessment stood out and merit a thorough evaluation.
The Court’s Narrow Take on the TSM Test
In its arguments, Jain Irrigation Systems not only denied infringement but also argued that the suit patent is invalid on the account of lack of novelty, absence of inventive step, and insufficient disclosure under Section 64 of the Patents Act, 1970. To buttress its claims, Jain Irrigation put forth several prior art documents, but considering the importance of these documents, the Court engaged in a case-by-case analysis of five prior art documents.
India follows the Teaching, Suggestion, or Motivation (TSM) approach, originating from the US case of KSR International v Teleflex Inc., as per the Delhi High Court decision in Avery Dennison Corporation v Controller of Patents and Designs. As per this approach, if an ordinary skilled person can modify the prior art reference or combine prior art references to arrive at the claimed invention – a process called mosaicing – then the subject matter being claimed is obvious. In Teleflex, the Court cautioned that the TSM test should be looked at broadly and not be muddled with a narrow interpretation – applicable to even those cases when the prior art is not designed to solve the same problem or for the same purpose (more can be read here and here).
Now, while the Court acknowledged the TSM approach, it interpreted it quite restrictively. The Court agreed that the elements of the suit patent were available in the market, however, it noted that they were for solving different purposes or different industries and not for tracking leakages or in the same market segment as the suit patent (paras 96-98).
It relied heavily on a narrow reading of the inventive step requirement, grounding its reasoning in the need to guard against hindsight bias – a tendency to view prior art and the invention in hand as obvious. This is to ensure that the inventive step is not applied in a retrospective manner, since the invention’s outcome is known, it becomes predictable to deconstruct the said invention and attribute its elements to prior art. To this end, the Court criticized Defendant’s reliance on distinct documents and added that none of the documents individually motivate the claimed mosaic (para 102). However, the absence of a single prior art showing the exact configuration does not defeat an obviousness case – what matters is if a PSA would be motivated to combine those prior arts. The Court’s assessment should have followed a combined-reference analysis rather than confining the inquiry to the disclosure of the invention by one document itself.
It also commented how none of the cited prior art references could motivate a person skilled in the art (PSA) to co-extrude a tracer cable on the outer surface of a metallic pipe to detect leakages (para 103). What it failed to recognize was that there could have been multiple motivations to co-extrude tracer wire onto the pipe surface, whether it be design simplicity, installation efficiency or cost reduction – an aspect also considered in Teleflex.
This trend of narrowly applying the TSM test has also been observed in Microsoft Technology Licensing LLC, where the obviousness standard was read narrowly, thereby contradicting the application of Teleflex (for further reading, here).
Conclusion
The Delhi High Court decision well distinguishes the difference between patent and design and effectively engages with this distinction. Further, it rightly applied the eye-test to this infringement case, in contrast to the abbreviated infringement inquiry, as in the Symphony cases, which have been taken up in the past few years. However, where it really missed the shot was its obviousness analysis of the suit patent. Its piecemeal approach to the TSM framework, followed by a narrow interpretation of mosaicing, is a string attached to the already growing number of decisions that hesitate to apply the obviousness test aptly.