New referral to the Enlarged Board of Appeal: G 1/26 on claim interpretation
Technical Board of Appeal 3.3.05 of the European Patent Office has referred a fundamental question of claim interpretation to the Enlarged Board of Appeal. The referral, pending as G 1/26 (“Coated steel strips”), concerns the role the description plays when assessing added subject-matter.
G 1/26: Claim interpretation under Article 123(2) EPC
The referral asks how far the description may be used when interpreting a claim. The Enlarged Board addressed this question in G 1/24, but did so in the context of patentability. G 1/26 raises the same question in a different context: added subject-matter under Article 123(2) EPC. The issue is which of a claim’s possible interpretations must be tested against the original disclosure.
The underlying case
The referral arises from an opposition against a European patent for coated steel strips (EP 3 587 104), which originated from a second-generation divisional application. The disputed feature is a titanium-to-nitrogen ratio. Claim 1 as granted requires the ratio to be “in excess of 3.42”, with no unit specified. However, the description — like the parent and grandparent applications — defines the ratio by weight. The opponent argues that omitting the unit broadened the claim beyond what was originally disclosed.
Three approaches to claim interpretation with differing outcomes
The Board identifies three approaches in the case law following G1/24 on how the description is used in claim interpretation. In the case at hand, these three approaches lead to two different outcomes.
Approach 1: Description used only to determine the skilled person
Under this approach, the description merely serves to establish the technical field and the common general knowledge. Read that way, the disputed ratio could be a molar ratio. Since this possibility was not originally disclosed, there would be added subject-matter; Article 123(2) EPC would be infringed.
Approach 2: No broadening or limitation of the claim based on the description
Here too, the unitless ratio covers a molar ratio as a possible reading, resulting in added subject-matter and an infringement of Article 123(2) EPC.
Approach 3: Holistic interpretation based on the patent specification as a whole
This approach allows the specification to narrow the claim. Since the relevant passages of the description define the ratio by weight, the feature is interpreted narrowly as a weight ratio. Under this approach, Article 123(2) EPC is satisfied.
An additional question on the admissibility of referrals
The Board also refers a separate question on the admissibility of referrals. In its view, a referral should be admissible where the point of law arises from the case and it is procedurally reasonable to decide that point first. What should not be required is ruling out every other objection to the patent beforehand.
Practical implications
The referral concerns a fundamental question of everyday patent practice. How a claim is to be construed, and which readings must find support in the original disclosure, often decides whether a patent survives. If the Enlarged Board finds the referral admissible, its answer will shape examination and opposition practice before the EPO. The proceedings will be worth following closely.
The full wording of the referred questions is available on the website of the European Patent Office. Closely linked to the questions raised here is referral G 1/25 on description adaptation, which addresses whether and to what extent the description must be aligned with amended patent claims.