Crystal Crop Protection Limited v. Safex Chemicals India Limited & Ors.

Relevant Acts and provisions

Patents Act, 1970

Section 108Section 48

Provisions considered: Sections 48 and 108 of the Patents Act, 1970, applying the doctrine of equivalents and prosecution history estoppel.

Brief facts

Crystal Crop Protection sued Safex Chemicals for infringement of its patent for a weedicidal formulation and method of manufacture, whose claims include a herbicide composition containing a dyeing agent or pigment. The defendants' competing formulation allegedly omitted this dyeing agent or pigment, and the plaintiff sought an interim injunction, invoking the doctrine of equivalents to argue that the element was non-essential.

Issues before the Court

1. Does omission of the dyeing agent or pigment from the defendants' product avoid infringement, applying the doctrine of equivalents and the essential-elements test?
2. Does the plaintiff's prosecution history, in which it relied on that element to establish patentability, estop it from now treating it as optional?

Court's findings

The Court held that the doctrine of equivalents cannot be invoked to read out an element that the complete specification itself identifies as central to solving the technical problem addressed by the invention; since the specification and the plaintiff's own submissions treated the dyeing agent or pigment as necessary for visible application and effective use of the weedicide, its omission could not be treated as an insubstantial variation.

The Court further held that prosecution history estoppel barred the plaintiff from now contending that the element was optional when it had relied on that very feature during prosecution to distinguish the invention from the prior art, and that the plaintiff could not approbate and reprobate.

Given disputed expert evidence on the element's significance, the Court held that the issues warranted trial rather than interim relief.

Decision

Application for interim injunction dismissed; the defendants were directed to maintain and periodically file accounts of manufacture and sale pending trial.

Keywords

Claim Construction Doctrine Of Equivalents Interim Injunction Patent Infringement Prosecution History Estoppel