Rethinking the Doctrine of Equivalence: Why Crystal Crop v Safex Risks Undermining the Gains of FMC v Natco

Introduction

What happens when someone copies the heart of your invention, but has evaded liability by omitting a component that, while mentioned in the patent claim, is functionally irrelevant? Crystal Crop v Safex risks allowing precisely that.

In FMC v Natco, the Delhi High Court took a meaningful step forward in how it thinks about patent infringement. Instead of analysing individual claim elements in isolation the Court focused on how the parts of an invention work together to produce a functional result. But in the recent ruling dated May 7^th, 2025 of the same court in Crystal Crop v Safex, that progress seems to have stalled.

The Dispute

Crystal Crop sought an interim injunction against Safex Chemicals. They alleged infringement of its patent titled “Weedicidal Formulation and Method of Manufacture Thereof” The suit patent (para 6.6) claimed a novel herbicidal mix of Clodinafop 9% and Metribuzin 20% in a 1:2.2 ratio, with a safener, surfactant, and optionally a dyeing agent. The formulation was described as essential to enhanced weed control, reduced phytotoxicity, and improved efficacy and yield. Crystal claimed that Safex’s products copied its formulation. Safex countered that their products did not infringe them as they lacked the dyeing agent referenced in the patent specification (Para 7.3) for visual tracking.

The Ruling and Reasoning

The Court declined the plaintiff’s plea for interim injunction, finding no infringement. Crystal argues that the real invention lies in the synergistic ratio and homogeneous wettable powder (para 8.1), and that the dye was non-essential, and that it had been included only for visual tracking (paras 8.2–8.3). However, the Court found the dyeing agent was essential under the Doctrine of Equivalents as it appeared in one claim and aligned with one of the patent’s stated objectives.

The Doctrine of Equivalence

India’s approach to the doctrine of equivalents has remained unsettled and is evolving. While earlier cases like Ravi Kamal Bali v Kala Tech did introduce a move toward a functional analysis, the jurisprudence largely has lacked direction.

FMC v Natco attempted to fill that gap by introducing an “interaction-based” test, one that assesses whether a claim element is essential not in isolation {The dye in this case} but rather is based on how it works in conjunction with other components to achieve the invention’s core [First evidenced in Para 34].

My submission is in line with the Court’s claim. Which is that this approach may offer an effective means of protection for process patents [Para 34, Natco].

However the decision is not without criticism. As Adarsh Ramanujan rightly points out in his commentary on patent law that FMC v Natco blurs the lines between two fundamentally different approaches to patent infringement. He observes that the judgment conflates two irreconcilable lines of thought the U.S. “all elements” rule (which requires strict equivalence for each claim element) and the UK’s earlier “pith and marrow” approach (which allows courts to discount non-essential elements. This creates avoidable uncertainty.

But if we look past the muddled synthesis, I argue that FMC may have still nudged Indian law in the right direction. FMC attempted to contribute towards a test tailored to the process and formulation patents. This asks whether the allegedly omitted or altered element actually contributes to the core inventive step. When seen in context, this is something neither the rigid “all elements” test nor the older essentiality test adequately handles.

Actavis and the Modern Test for Equivalence

That reasoning infact somewhat aligns with the UK Supreme Court’s formulation in Actavis v Eli Lilly (2017), which shifted away from literalism toward a more holistic inquiry.

1. i) Notwithstanding that it is not within the literal meaning of the relevant claim(s) of the patent, does the variant achieve [2017] UKSC 48 substantially the same result in substantially the same way as the invention, i.e. the inventive concept revealed by the patent?
2. ii) Would it be obvious to the person skilled in the art, reading the patent at the priority date, but knowing that the variant achieves substantially the same result as the invention, that it does so in substantially the same way as the invention?
3. iii) Would such a reader of the patent have concluded that the patentee nonetheless intended that strict compliance with the literal meaning of the relevant claims of the patent was an essential requirement of the invention?

Actavis emphasises that the patent scope cannot be limited to claim language alone. What matters is how a skilled person would interpret the functional significance of the variation. Yet, Actavis has had its limitations particularly for complex chemical or process patents. It lacked clarity on how courts should assess immaterial variations especially in process-heavy cases. As Ramanujan notes, the post-Actavis world is murkier than ever.

This is precisely where FMC makes a contribution. Its interaction-based approach addresses that ambiguity by focusing not on whether an element appears in the claim language, but whether it functions within the inventive concept.

I will demonstrate that Crystal Crop purported to rely on both FMC and Actavis. However, it failed to apply either. The Court treated the dye as essential simply because it was listed in the claims and mentioned among the objectives without examining whether it was actually integral to the invention’s function.

I argue that the court subtly reverted the focus to the presence or absence of specific claim elements. This is in contrast to evaluating how those elements function together within the invention as a whole. Instead of assessing the composition’s interactive functionality, the Court isolated the dyeing agent and treated its omission as determinative, despite the defendants having replicated the core chemical formulation and its primary functional objectives {As I will demonstrate later in this post}

Essentiality in a Vacuum

In Crystal Crop, the Court appears to treat the dyeing agent as essential largely because it was listed as one of the invention’s objectives. But that inference doesn’t hold up when the patent is read in its entirety.

As set out in para 20, the Background of the Invention identifies five core problems the patent seeks to solve but only one of which relates to visual detection. The others concern:

1. the lack of homogeneous herbicidal compositions with synergistic effects;
2. phytotoxicity;
3. poor adherence of herbicides to weed surfaces; and
4. the limited efficacy of existing formulations against common wheat weeds like Phalaris minor and Avena fatua.

To this one might argue that even if a component is mentioned only once in the specification it could still prove essential to the invention. But that question cannot be answered in isolation. It hinges on how the component interacts with the rest of the invention – which is precisely the kind of function-based, interaction-driven analysis articulated in FMC v. Natco.

Applied here, the answer is clear: the dye was not functionally central. It didn’t influence the chemical synergy, enhance efficacy, or reduce phytotoxicity i.e the key elements that formed the inventive heart of the suit patent.

A closer look at the objectives confirms this. Each of the other five objectives supports the view that the invention’s core lies in the chemical formulation {Para 23}:

1. Objective {a}: Low-dose effectiveness {points to the enhanced efficiency of the Clodinafop-Metribuzin combo, not something influenced by a dye.}
2. Objective {b}: Developing a homogeneous wettable powder to address the problem of uneven application {para 20}. {which is tied more to ingredient compatibility, not visibility}.
3. Objective {c}: To provide a method for the preparation of a homogeneous wettable powder herbicide {again not dependent on whether or not it’s coloured.}
4. Objective {d}: Improved adherence to weed surfaces {functional outcome of the formulation and surfactants, not the presence of a dye.}
5. Objective {f}: Controlling resistant weeds like Phalaris minor {achieved through the synergistic action of the specific chemical ratio, again, independent of any visual cue.}

Taken together, this means that five out of six objectives, and the bulk of the claim specifications are directly dependent on the chemical synergy of Clodinafop Propargyl and Metribuzin in a 1:2.2 ratio {Plaintiff’s Claim}, and not the presence/ absence of a dye which is merely a visual cue. This makes it clear that the dye was not part of the invention’s functional core. It was an auxiliary feature at best.

Even the court in para 25 describes the dye as only ‘one of the embodiments of the invention’. This would confirm that the dye was merely one amongst many other features of the formulation and not its core.

Drawing from the amicus brief submitted in the landmark U.S. Supreme Court decision in Warner-Jenkinson equivalence should be denied only when:

1. The accused product is materially different;
2. The omitted component adds independent value or alters function; or
3. It was excluded to avoid prior art.

None apply here. The dye wasn’t replaced or improved. The core chemical logic—Clodinafop and Metribuzin in a 1:2.2 ratio was copied outright. Even if the dye helped with field use, it didn’t influence performance.

{And yes, this is a layperson’s interpretation, but since Justice Bansal chose to defer expert opinion to trial and rely on his own reading at the interim stage, a close, reasoned engagement with the patent text is not only permissible, it’s appropriate.}.

Even if the Court’s view that the dye aided visual assessment is accepted {para 26} this still would not make it central to the invention’s inventive concept. Its limited influence over majority of the patent’s objectives confirms it was a secondary and non-inventive feature.

In sum, I establish that: the dye may have served relevant purpose. But as long as that purpose was not inventive i.e somehow change the synergy of the composition itself it should not affect this analysis. Under the doctrine of equivalents, what matters is a component’s contribution to function, not mere inclusion. The defendants copied the functional core and omitted only a cosmetic element. That’s the very mischief the doctrine aims to prevent.

The Grey Zone Post-Crystal Crop

Existing tests like Actavis guard against obvious tweaks to evade patents. But the real challenge lies in a grey zone i.e where an omitted element is neither essential nor wholly irrelevant. That’s where Crystal Crop stumbles. Though it cited both FMC and Actavis, it failed to apply either meaningfully. It relies instead on the element’s presence in the claim rather than its functional role in the invention.

This is the ambiguity FMC tried to address. While it may have blurred the U.S. “all elements” rule and the UK’s pith and marrow test, it proposed an interaction-based approach that offers a more practical framework for complex chemical patents.

Crystal Crop thus risks opening the door to a loophole where strategic circumvention through such grey area omissions may bypass patent protection even as the invention’s substance has been copied. The dilemma, therefore, isn’t of minor and irrelevant deviations. But it is with regard to how we treat partially relevant changes. That choice will shape the future of patent protection, especially in complex chemical cases.

(This post has been authored by Yohann Titus Mathew is a fourth-year B.Sc. LL.B. (Hons.) [Cyber Security] student at the National Law Institute University, Bhopal.

CITE AS: Yohann Titus Mathew ‘Rethinking the Doctrine of Equivalence: Why Crystal Crop v Safex Risks Undermining the Gains of FMC v Natco’ (The Contemporary Law Forum, 16 August 2025) <https://tclf.in/2025/08/16/rethinking-the-doctrine-of-equivalence-why-crystal-crop-v-safex-risks-undermining-the-gains-of-fmc-v-natco/> date of access.