Onus to Prove Patent Invalidity Rests on Defendant, Infringement is Product-to-Patent: Delhi HC While Remanding Injunction Plea - 2025-09-26

Delhi High Court Sets Aside Order Vacating Patent Injunction, Clarifies Two-Step Test for Infringement Suits

New Delhi: The Delhi High Court, in a significant ruling on patent infringement litigation, has set aside a Commercial Court's order that had vacated an interim injunction. The Division Bench of Justice C. Hari Shankar and Justice Ajay Digpaul held that the lower court had fundamentally erred in its legal approach by failing to properly assess infringement and by incorrectly shifting the burden of proof regarding the patent's validity onto the plaintiff.

The High Court restored the temporary injunction in favour of the appellant, Mold Tek Packaging Limited, and remanded the matter for fresh consideration, laying down a clear framework for analyzing interim injunction applications in patent disputes.

Background of the Dispute

The case, Mold Tek Packaging Limited v. Pronton Plast Pack Pvt. Ltd. , revolves around two patents (IN 401417 and IN 298724) held by Mold Tek for its "Tamper Evident Leak Proof Pail Closure Systems" and a "Tamper Proof Lid Having Spout." These patented lids are designed to be tamper-proof and tamper-evident, featuring unique locking lugs and a tear band.

Mold Tek had secured an ex-parte interim injunction on December 20, 2023, restraining Pronton Plast from manufacturing and selling products that allegedly infringed on these patents. However, on May 2, 2024, the Commercial Court vacated this injunction after Pronton Plast filed an application under Order XXXIX Rule 4 of the Code of Civil Procedure, 1908. Mold Tek subsequently appealed this vacation order to the High Court.

Core Arguments Before the High Court

Appellant's Contentions (Mold Tek): Senior Advocate Mr. Jayant Mehta, representing Mold Tek, argued that the Commercial Court's order was "completely unreasoned." He contended that the lower court failed to conduct the necessary analysis of whether the respondent's product infringed the appellant's patent claims. He stressed that the correct comparison is between the defendant's product and the patent's complete specifications (a "product-to-patent" analysis), not between the two parties' products ("product-to-product"). Furthermore, he argued that the lower court wrongly placed the onus on the plaintiff to prove the novelty of its invention, contrary to the established principles under the Patents Act, 1970.

Respondent's Contentions (Pronton Plast): Senior Advocate Mr. J. Sai Deepak, for Pronton Plast, conceded that the impugned order "may not be as reasoned as such orders ordinarily ought to be." However, he defended the lower court's finding on the burden of proof, arguing that since Mold Tek claimed its patent was an "improvement" over prior art, the onus was on them to prove it.

High Court's Two-Step Framework for Infringement Analysis

The Division Bench found the Commercial Court's order legally unsustainable and used the opportunity to clarify the two essential aspects a court must consider in patent infringement actions.

1. The Test for Infringement

The Court reiterated that the first step is to determine if the defendant's product infringes the plaintiff's suit patent. It emphasized a crucial, often overlooked, principle:

"The comparison has to be product-to-patent and not product-to-product. What is prohibited, by Section 48, is the making, using, offering for sale, selling or importing of the product which forms 'subject matter of' the patents held by another... The Court as to compare the goods of the defendant with the subject matter of the suit patent, as is contained in the complete specifications of the suit patent."

The bench found that the lower court had failed to undertake this mapping exercise and had erroneously accepted the defendant’s mere "argument" of dissimilarity as a "valid credible defence."

2. Credible Challenge to Patent Validity and Onus of Proof

The second step, triggered when a defendant raises a defence under Section 107 of the Patents Act, is to assess whether a "credible challenge" has been made to the patent's validity. The High Court clarified that the onus for this rests squarely on the defendant.

"Once the plaintiff has succeeded in discharging its initial onus to establish that the defendant’s product infringed the plaintiff’s suit patent, the onus on the plaintiff stands discharged... the onus to establish that the plaintiffs’ suit patent was vulnerable to invalidity for one or more of the grounds envisaged by Section 64 is wholly on the defendant. In an infringement action, it never shifts."

The Court held that the Commercial Court had "fundamentally in error" by holding that the plaintiff had the initial burden to establish novelty.

Final Decision and Implications

Finding that the Commercial Court had failed on both analytical fronts, the High Court quashed and set aside the order dated May 2, 2024. Consequently, the original ex-parte ad interim injunction granted on December 20, 2023, was restored and will remain in effect pending a fresh decision.

The matter has been remanded for de novo consideration by a learned Single Judge of the High Court, as the case was transferred following the filing of a counterclaim. The parties have been directed to appear before the Single Judge on July 25, 2025, for an expedited hearing on the injunction application.

This judgment serves as a crucial guide for lower courts, reinforcing the structured, two-step legal framework for adjudicating interim relief in patent infringement suits and clarifying the distinct roles and burdens of the plaintiff and defendant.