Broadening by Ambiguity: T 0977/25 on Claim Interpretation and Article 123(2) EPC
In T 0977/25, the EPO Board of Appeal clarified that an unresolved ambiguity in an amended claim results in a broader interpretation, not an open one. This broader scope can trigger an infringement of Article 123(2) EPC.
Picture drafting a method claim for manufacturing a two-part device, specifying only that a storage portion and a heater assembly are "provided". You might assume the skilled person will naturally infer that these components are eventually fixed together to form the final product. However, as the patent proprietor in T 0977/25 discovered, relying on the term "providing" without explicitly claiming the assembly step leaves the claim vulnerable to a much broader interpretation, even when read in light of the description.
Why did the Board find that the method of manufacturing in the main request lacked novelty?
Claim 12 of the main request defined a method comprising providing a storage portion and providing a heater assembly. The proprietor argued that the skilled person would understand this as relating to the manufacture of a cartridge where the heater assembly is fixed to the storage portion, asserting this was the only technically reasonable interpretation supported by the description.
The Board disagreed. The notion of "providing" per se covers the mere act of making available and does not imply that the components are fixed together (reasons 5). Applying the principles of G 1/24, the Board consulted the description but found no passage stating that the heater assembly had to be fixed to the housing during manufacture (reasons 7.2). Consequently, the claim was interpreted broadly. Document D3 disclosed a storage portion and a heater assembly arranged next to each other. Because the claim did not prescribe any particular manner of assembling these components, the Board concluded that the subject-matter of claim 12 lacked novelty over D3 (reasons 11).
How did an ambiguous pronoun trigger an infringement of Article 123(2) EPC?
To overcome the novelty objection, the proprietor amended claim 12 in auxiliary request 1 to specify fixing a heater assembly comprising at least one heater element to the open end of the housing so that "it" extends across the opening.
The opponent argued that the pronoun "it" rendered the claim ambiguous. Grammatically, "it" could refer either to the heater assembly (scenario A) or to the heater element (scenario B). The Board found that both possibilities were compatible with the technical context and conveyed a clear technical teaching (reasons 27). While the application as filed directly and unambiguously disclosed scenario B, it did not explicitly or implicitly disclose the entire heater assembly extending across the opening as required by scenario A (reasons 29).
Does the gold standard require resolving ambiguities to save a claim?
The Board acknowledged conflicting case law regarding how claim interpretation interacts with Article 123(2) EPC in the case of ambiguous claims. Some previous decisions suggested that an ambiguity must first be resolved by interpretation before compliance with Article 123(2) EPC can be assessed, implying a claim should be interpreted in a way that avoids non-compliance.
The Board explicitly rejected this approach. Compliance with Article 123(2) EPC cannot be a precondition for correct claim interpretation, as this would contradict the underlying rationale of the gold standard established in G 2/10 (reasons 31). Crucially, the Board held that leaving an ambiguity in a claim unresolved is not tantamount to leaving its interpretation open (reasons 32). Instead, an unresolved ambiguity may simply result in a broader interpretation. By interpreting the claim to encompass both scenario A and scenario B, the Board found that the broader scope covered a scenario not directly and unambiguously derivable from the application as filed, thereby infringing Article 123(2) EPC (reasons 34).
Why was the etching gap in D4 not considered an aperture of a different size?
After the proprietor deleted the method claims in auxiliary request 1', the opponent maintained a novelty attack against the apparatus claim over document D4. The opponent argued that a gap formed by etching between conductive filaments and electrical contacts constituted an aperture of a different size, which would deprive the claimed heater element of novelty.
The Board rejected this reading. The gap was a structural necessity of the etching process to prevent a short-circuit, and the skilled person would not attribute any function to it different from contact gaps in other embodiments (reasons 41). The contacts formed part of the heater assembly, not the heater element itself. Therefore, the apertures of the heater element in D4 were only the uniform spaces between the filaments, rendering the claim novel.
How should practitioners handle ambiguous claim amendments after T 0977/25?
When introducing pronouns or relative clauses during opposition proceedings, practitioners should carefully check all grammatical antecedents. Practitioners should not rely on the description or the requirement to comply with Article 123(2) EPC to retroactively narrow an ambiguous term to a single allowable interpretation. If an amendment creates a grammatically valid but undisclosed alternative, the resulting broader scope may infringe Article 123(2) EPC. Practitioners should ensure that every possible grammatical reading of an amended feature is directly and unambiguously derivable from the application as filed.
Sources
Further Reading
Articles related to the topics covered above.
Resolving Ambiguity Under Article 123(2) EPC: T 0392/25 on Combinatorial Amendments
Technical Board of Appeal 3.4.02 clarifies that an ambiguous description passage cannot provide a basis for an amendment merely because the claimed combination represents one possible interpretation.
Applying G 1/24 to Added Matter: T 0873/24 Refers Claim Interpretation
Board 3.3.05 has referred fundamental questions to the Enlarged Board of Appeal regarding how G 1/24 applies to Article 123(2) EPC, alongside a challenge to the strict admissibility threshold for referrals.
G 2/10 and Selections from Lists: T 0201/24 on Added Matter in Divisional Applications
In T 0201/24, the EPO Technical Board of Appeal clarified that applying the gold standard of G 2/10 does not preclude assessing added matter through selections from lists. The decision highlights the strict requirements for combining component ranges.