The end of the Reproducibility Fiction: how the EBA Decision G 1/23 transforms prior art assessment

Historical context

The European Patent Convention (EPC)  determines which inventions deserve protection by comparing them against “the state of the art". Article 54(2) EPC  states that prior art includes “everything made available to the public by means of a written or oral description, by use, or in any other way, before the date of filing of the European patent application”.

 While this article seems straightforward, the 1992 decision of the EPO’s Enlarged Board of Appeal (EBA) G 1/92 created a strict requirement with some ambiguity by establishing that "the chemical composition of a product is state of the art when the product as such is available to the public and can be analysed and reproduced by the skilled person, irrespective of whether or not particular reasons can be identified for analysing the composition". This formulation created what became known as the "reproducibility requirement," establishing a dual condition that a disclosed product must be both analysable and reproducible by the skilled person without undue burden in order to qualify as prior art. 

Over the following decades, subsequent Technical Boards of Appeal (TBA) have interpreted this decision in different ways. Some Boards decided that if a product could not be reproduced, it should be completely ignored as prior art when evaluating new patent applications - as if the commercially available product simply did not exist, creating what G 1/23 termed a "legal fiction". Other Boards took a less stringent approach, excluding only the non-reproducible aspects while considering the remaining product features as prior art.

The case that changed everything

The confusion reached a breaking point in T 0438/19 (the case underlying this referral) relating to European Patent No. 2626911, owned by Mitsui Chemicals. This patent claimed a specific type of polymer material used to encapsulate solar cells, with the particular requirement that it needed to include an aluminium content within a certain defined range. The key issue for patentability was the inventiveness of the claim over an example in a prior art document (example 3 of D1) that included a commercially available polymer called ENGAGE® 8400, which had been sold on the market before Mitsui's patent application was filed.

Technical documentation showed that ENGAGE® 8400 used in example 3 of D1 possessed all of the properties claimed in Mitsui's patent, except that its aluminium content was different. While the ENGAGE® 8400 product was readily available for purchase and its properties were well-documented, its manufacturing method was not in the public domain and reproducing the product would be challenging for experts in the field, particularly because the necessary catalyst was not disclosed.

Mitsui argued that example 3 of D1 should be discarded as prior art because ENGAGE® 8400 could not be exactly reproduced, relying on the seemingly strict reproducibility requirement of the G 1/92 decision. The opposing party, Borealis GmbH, maintained that a commercially available product should not be ignored simply because its manufacturing method was not known.

This discussion highlighted the fundamental absurdity of the existing legal fiction. ENGAGE® 8400 was a marketed product, sold together with extensive technical documentation describing its properties and applications. Treating such products as "non-existent" for patent purposes contradicted both commercial reality and common sense.

The TBA in its decision T 0438/19 recognized that this issue affected far more than just this single patent dispute. The inconsistent application of the reproducibility requirement was creating uncertainty throughout the European patent system. Accordingly, the Board asked the EBA to provide definitive guidance.

The EBA has now delivered a comprehensive decision that fundamentally restructures how European patent law treats commercially available products. The EBA answered the central question as to whether products placed on the market before a patent filing date can be excluded from the prior art solely because they cannot be analysed and reproduced with an unambiguous “No”.

Central to the decision was the reinterpretation of what "reproducibility" means in European patent law. A  distinction was made between obtaining a product "in its readily available form" versus reproducing it "by a different method" using alternative starting materials and manufacturing processes. The EBA determined that the reproducibility requirement is automatically satisfied for products sold on the market because experts can always obtain the physical product through purchase or other market mechanisms.

The decision also addresses whether technical information about non-reproducible products should be considered prior art. The Board ruled that publicly available technical information about such products forms part of the state of the art regardless of whether the product itself can be reproduced. This acknowledges that modern product commercialization typically involves extensive documentation, performance specifications, and application guidelines that provide valuable technical knowledge independent of manufacturing reproducibility.

The Board also clarified that products do not lose their prior art status if they later disappear from the market or undergo modification. Once a product becomes publicly available, it permanently becomes part of the state of the art for future patent applications. This principle aligns with established precedents regarding internet disclosures and other temporarily available prior art, as exemplified in T 1553/06, and prevents companies from gaming the system by temporarily withdrawing products to avoid prior art implications.

What this means for patent practice

G 1/23 fundamentally affects strategic considerations for commercialisation and patent filing across all industries. The decision confirms that securing patent protection before any form of public product disclosure is crucial, regardless of whether competitors can easily reverse-engineer the technology or product. Companies can no longer rely on manufacturing complexity or proprietary processes to preserve patentability after product launch.

Under this decision, every commercially released product constitutes comprehensive prior art citable against later filed patent applications, regardless of the  complexity of reproduction. Enhanced coordination between research and development, legal, and marketing teams is all the more essential to ensure patent applications are filed before making public disclosures, and definitely before commercialisation.

For companies developing improvements to existing commercial products, G 1/23 also means that all analysable properties of the original product are clearly part of the state of the art. This may require more specific patent claim language to distinguish patentable improvements from the underlying commercial product.

Although at first sight G 1/23 may seem harsh on patentees, it ultimately strengthens the European patent system by eliminating legal fictions that separated European patent law from commercial and technical reality. The decision ensures that the state of the art encompasses all information made available to the public, consistent with the fundamental purposes of patent law: rewarding genuine innovation while preventing the grant of patents that would restrict access to information already in the public domain.

Should you have any questions arising from this decision, please do not hesitate to contact us at info@dcp-ip.com