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.
The strictness of the gold standard for assessing added matter under Article 123(2) EPC has long required that amendments be directly and unambiguously derivable from the application as filed. The boundary between a permissible interpretation of a broad disclosure and an impermissible selection from an ambiguous passage is frequently tested in European patent practice. In T 0392/25, Technical Board of Appeal 3.4.02 clarifies this boundary by holding that an ambiguous description passage cannot serve as a basis for an amendment simply because the claimed combination represents one possible reading.
Why did the combination of location and transparency adjustments trigger an added matter objection?
The application concerns a method for an augmented reality display on a vehicle windscreen. During examination, the applicant amended claim 1 to require two simultaneous measures to prevent the occlusion of environmental features the operator needs to see. Specifically, the method required determining a location for an attribute image (Feature A) and adjusting the luminosity and/or transparency of that attribute image (Feature B).
To support this combination, the applicant relied on paragraph [0033] of the application as originally filed. This paragraph stated that a location of an attribute can be designated to prevent occlusion of an object, and that a luminosity and/or a transparency of an attribute image can "also" be adjusted to prevent obstruction. The examining division refused the application, finding that this paragraph left too much room for interpretation regarding how the two features related to each other.
How does the Board evaluate the word "also" under the gold standard?
The Board agreed with the examining division that paragraph [0033] was ambiguous. The text allowed for three different interpretations: the measures could be cumulative, they could be alternatives, or the passage could disclose both the combination and the selection.
While the word "also" indicates a further possibility, the Board found that it does not clearly and unambiguously establish that the transparency adjustment is performed in addition to the location designation (reasons 1.6.2). Crucially, the Board held that an ambiguous passage in the description cannot provide a direct and unambiguous basis for an amendment merely because the claimed subject-matter corresponds to one possible interpretation of that passage (reasons 1.6.3). For a combination of features to be directly and unambiguously derivable, the skilled person must be able to recognise it as part of the technical teaching without having to resolve an ambiguity by selecting one of several possible interpretations.
Why did the applicant's synergistic effect and anticipation arguments fail?
The applicant attempted to overcome the ambiguity by arguing that the two measures provided a synergistic effect. For example, if an object was too large to avoid by adjusting the image location alone, reducing the transparency would further improve perception. According to the applicant, this synergy meant the skilled person would understand the measures as being used in conjunction.
The Board rejected this reasoning. The alleged synergistic effect merely suggests that combining the two measures would be technically advantageous, which might motivate a skilled person to consider such a combination (reasons 1.9.1). However, technical advantage does not establish that the combination itself forms part of the technical teaching directly and unambiguously derivable from the application as filed. The Board similarly dismissed the applicant's argument that paragraph [0033] would anticipate the claim if it were prior art, noting the logical flaw: if the passage does not directly and unambiguously disclose the combination, it cannot anticipate it (reasons 1.9.4).
What must practitioners change when relying on "also" for claim amendments?
European patent attorneys must recognise that sequential sentences linked by "also" do not automatically provide a valid basis for a combinatorial amendment under Article 123(2) EPC. When drafting a European patent application, practitioners should explicitly state when features can be used "in combination with" one another, rather than merely listing them as additional possibilities.
During prosecution, this decision demonstrates that arguing technical sensibility or synergistic effects cannot cure a linguistic ambiguity in the original disclosure. If the skilled person must resolve an ambiguity to arrive at the claimed combination, the amendment will fail the gold standard. Applicants and patent proprietors defending amendments must ensure that the original text stands on its own as a clear disclosure of the specific combination, without requiring the reader to select the cumulative interpretation from a set of equally valid alternatives.
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