By Jigyasa Pareek

In a significant batch of decisions pronounced on October 9, 2025, the Delhi High Court undertook a comprehensive interpretation of Section 3(i) of the Patents Act, 1970, which excludes “any process for the medicinal, surgical, curative, prophylactic, diagnostic, therapeutic or other treatment of human beings or any process for a similar treatment of animals to render them free of disease or to increase their economic value or that of their products” from patentability.

Justice Prathiba M. Singh’s judgments in Sequenom Inc. & Anr. vs Controller of Patents [C.A.(COMM.IPD-PAT) 13/2022 and 448/2022], EMD Millipore Corporation vs Assistant Controller of Patents and Designs [C.A.(COMM.IPD-PAT) 7/2021], and Natera Inc. & Anr. vs Assistant Controller of Patents and Designs [C.A.(COMM.IPD-PAT) 16/2023], together form a landmark pronouncement on the boundary between non-patentable diagnostic processes and patentable diagnostic inventions.

The rulings clarify the legislative intent behind Section 3(i), its relationship with international patent norms, and the scope of what is excluded from patent protection under Section 3(i).

I. Legislative History of Section 3(i): From “Manner of Manufacture” to Modern Exclusion

1. The 1911 Act and the Ayyangar Committee Report

Under the Patents and Designs Act, 1911, patentability hinged on the existence of “a novel method of manufacture”. Therefore, although not expressly excluded, medical, surgical, curative, prophylactic and therapeutic processes or methods were regarded as non-patentable.

Justice Rajagopala Ayyangar’s 1959 Report recommended that this implicit exclusion be expressly codified. In paragraphs 327–332, the Committee observed that “processes for medicinal, surgical, curative, prophylactic and other treatment of man and processes for similar treatment of animals or plants” should be categorically excluded from patent protection.

2. Section 3(i) in the 1970 Act

The 1970 Act incorporated this exclusion almost verbatim. Section 3(i) thus exempted from patentability processes of treatment of humans, animals, or plants. The exclusion was limited to processes, not products.

3. The 2002 Amendment and India’s TRIPS Commitments

During TRIPS negotiations, India had suggested adopting Article 52 of the European Patent Convention (EPC) 1973, which excluded only methods “practised on the human or animal body”. Under that model, in vivo methods (performed on the body) were excluded, but in vitro diagnostic methods (performed on samples outside the body) were patentable.

However, the final TRIPS Agreement under the Article 27.3 (a) made no such distinction between in vivo and in vitro methods. Consequently, the 2002 amendments to the Indian Patents Act introduced the words “diagnostic” and “therapeutic” into Section 3(i). The term ‘or plants’ was thereafter deleted from Section 3(i) and incorporated separately in Section 3(j).

4. Patent Office Practice and the Manual

The Manual of Patent Office Practice and Procedure (2019) defines a diagnostic method as “the identification of the nature of a medical illness, usually by investigating its history and symptoms and by applying tests”. Determining general physical condition (e.g., a fitness test) is also treated as diagnostic. The Manual illustrates that:

• Methods of treating or operating upon humans or animals (such as cosmetic treatment, termination of pregnancy, castration, sterilization, artificial insemination, embryo transplants, treatments for experimental and research purposes, removal of organs from a living donor, any therapy or diagnosis practiced on the human or animal body and further includes methods of abortion, induction of labour, control of estrus or menstrual regulation) are not patentable;
• Application of substances to the body for purely cosmetic purposes is not therapy.
• Instruments, apparatus, prostheses, or artificial limbs, as well as measurements taken on the body to design them, may be patentable.

Despite these clarifications, the Patent Office has often applied Section 3(i) broadly to any invention remotely connected with diagnosis, creating uncertainty. This inconsistency set the stage for judicial intervention.

II. Comparative Jurisprudence: UK and European Approaches

The Court examined how similar exclusions are interpreted in other jurisdictions:

1. The United Kingdoms

Section 4A(1) of the UK Patents Act 1977 excludes: “a method of treatment of the human or animal body by surgery or therapy, or a method of diagnosis practised on the human or animal body”.

The exclusion is confined to methods, not to products or tools used in diagnosis or treatment. The objective is to ensure doctors’ freedom to practise medicine, not to restrict the patentability of medical technology.

2. The European Patent Convention

Article 53(c) of the EPC, 2000, contains an identical exclusion: “methods for treatment of the human or animal body by surgery or therapy and diagnostic methods practiced on the human or animal body; this provision shall not apply to products, in particular substances or compositions, for use in any of these methods”. The EPO’s Enlarged Board of Appeal has, over time, articulated clear tests for its application:

• Case Number G 0001/04: A diagnostic method must include all four essential steps:
  • Examination and data collection,
  • Comparison of data with standard values,
  • Identification of deviation, and
  • Deductive medical or veterinary decision.

Only if all these steps are carried out on the body and culminate in a diagnosis does the exclusion apply. Partial steps or methods performed in vitro, are not excluded. Whilst the surgical or therapeutic nature of a method claim can be achieved by a single method step, several method steps are required to define a diagnostic method due to the inherent and inescapable multi-step nature of such a method.

• Case Number G0001/07: “Treatment by surgery” are excluded only when they involve substantial health risks even when carried out with the required professional care and expertise. Routine or cosmetic procedures performed on uncritical body parts and generally carried out in a non-medical, commercial environment (tattooing, hair removal, etc.) fall outside the exclusion.

Together, these rulings clarified that the exclusion is restricted to core clinical acts performed on the body, to provide immunity to medical practitioners. For instance, if a method is developed for diagnosing diabetes, which is non-invasive (in vitro) in nature, it can be patented in the European Union and the United Kingdom.

III. Key Observations made by the Delhi High Court

Having reviewed the legislative background and comparative jurisprudence, the Delhi High Court distilled guiding principles to interpret Section 3(i) in light of modern patent law and the evolved definition of “invention” under Sections 2(1)(j) and 2(1)(ja).

The Court observed that, following the 2002 amendments, patentability is no longer confined to “methods of manufacture”; both products and processes are patentable so long as they are novel, inventive, and industrially applicable. Accordingly, Section 3(i) must be read in harmony with this expanded framework as a narrow exclusion.

1. Purpose of the Exclusion: Protecting Medical Autonomy

The Court reaffirmed that the central object of Section 3(i) is to safeguard the autonomy of medical professionals who interact directly with human or animal bodies in the course of diagnosis or treatment.

The exclusion was never designed as a blanket prohibition on patenting inventions related to healthcare. Instead, its purpose is to prevent patents from monopolising core medical and clinical activities that doctors are specifically trained and legally liable to perform.

In other words, Section 3(i) protects the freedom to perform essential medical procedures, not to innovate in health related technology.

The Court further emphasized that Section 3(i) is confined to process claims, not product claims. Thus, tools and products irrespective of whether they are in vivo or in vitro are entitled to grant of patent even if they can be used in the process of performing surgery, diagnosis or therapy.

Additionally, novel methods for performing cosmetic procedures such as a hair removal technique are not excluded from patentability. The distinction lies in the purpose, context, and nature of the intervention: whether the method pertains to core medical activity and requires professional judgment and carries inherent risk, or whether it is a low-risk, routine, commercial procedure commonly performed in non-medical, commercial settings.  

2. The Scope of Section 3(i)

Products, processes, or tools used by professionals that assist in diagnosing, treating, performing surgeries or in therapy are not excluded from patentability. What is excluded are the processes performed by medical professionals in implementing these tools or products as part of treatment or diagnosis.

Further, a new process, which may be devised for diagnostic purposes either in the form of a product cum process, a product per se, would be patentable.

Processes and Methods That Are Excluded

The Court clarified that the exclusion under Section 3(i) covers:

• Processes or methods for diagnostic or therapeutic purposes performed by medical professionals during treatment or diagnosis;
• Process or method involving physical or invasive intervention in the patient’s body, such as surgical stitching or wound closure;
• Therapeutic treatments, including both curative and prophylactic therapies;
• Methods which directly implicate professional judgment and involve invasive or high-risk procedures; and
• Processes for administration of medicines, whether oral, intravenous, topical, transdermal, subcutaneous, etc.; and
• Mere identification of the regimen for the use of certain medicines in a particular manner or frequency or form

In these cases, the process itself, being an integral part of medical or clinical practice, is not patentable, irrespective of the tools used to perform it.