Crystal Crop Protection Limited vs. Safex Chemicals India Limited

The Delhi High Court applies prosecution history as an estoppel in a patent infringement analysis to prevent a patentee from using the doctrine of equivalents (DoE) to recapture subject matter surrendered from the literal scope of a claim during prosecution.

The ruling emerged from an interim injunction application filed by Crystal Crop Protection Limited, seeking to restrain Safex Chemicals India Limited and its affiliates from infringing its patent (No. 417213) titled “Weedicidal Formulation and Method of Manufacture thereof.” The asserted patent comprised a herbicidal composition containing Clodinafop, Metribuzin, a surfactant, a dyeing agent or pigment, and a safener.

The dyeing agent or pigment’ was absent in the infringing product. So, to establish infringement, the patentee averred that the ‘dyeing agent or pigment’ was non-essential and an optional feature of the asserted patent. And that, the absence of the ‘dyeing agent or pigment’ in the Defendants’ product did not rule out infringement by equivalence.

In response, the Defendants contended that the ‘dyeing agent or pigment’ was explicitly included as an essential feature in the patent claims and played a vital role by enabling visual identification of treated areas. Since their products did not employ the ‘dyeing agent or pigment’ there was no infringement - literal or by equivalence.

The Court noted:

- In infringement analysis by DoE, the test is whether the variant achieves substantially the same result in substantially the same way as the patented invention

- Upon examining the claims, complete specification, and prosecution history, it was found that the ‘dyeing agent or pigment’ was an essential element of the patented invention and that the grant was given based on the uniqueness of the invention owing to the presence of the 'dyeing agent or pigment'. So, later in the infringement suit, the patentee cannot take a contrary stand – one cannot approbate and reprobate.

- Once the patentee includes a feature in the independent claim(s) and assigns it a vital role during prosecution, it cannot subsequently argue the feature is non-essential. The principle of prosecution estoppel was applied in the infringement assessment.

- The 'dyeing agent or pigment' performed a specific function in the patented invention; it solved a problem identified in the prior art and was directly tied to one of the objectives of the invention. The absence of the ‘dyeing agent’ would alter not only the formulation but also the very objective and utility of the invention. Accordingly, the absence of 'dyeing agent or pigment' in the infringing product, causes the infringement by equivalence allegation to fail.

The decision highlights the importance of claim drafting and consistent characterization of essential features during patent prosecution. Further, it underscores that patentees are bound by their submission(s) during prosecution, highlighting the critical role of prosecution history estoppel.

Crystal Crop Protection Ltd. v. Safex Chemicals India Ltd. & Ors., CS(COMM) 196/2024

Click here to read the judgement copy.