In the decision Scheinwerferbelüftungssystem (X ZR 16/17), the German Federal Court of Justice was concerned with the issue of claim interpretation in terms of prior art described in the patent. As a general principle, highlighted in the decision, it must be considered for claim interpretation that a patent with its teaching seeks to delimit itself from prior art described therein. In particular, if the content of a state of the art description is equated with the preamble of a patent claim, the features of the characterising portion must, in case of doubt, not be construed as being part of the subject matter of the state of the art from which they shall differ.
Such claim interpretation finds its legal basis in the second sentence of paragraph 14 of the German Patent Act (corresponding to Article 69(1) EPC), hence "the description […] shall be used to interpret the claims". Prior art described in the patent has also been considered in claim interpretation in several previous decisions of the German Federal Court of Justice (e.g. BGH X ZR 37/76 - Stromwandler, BGH X ZR 45/85 - Befestigungsvorrichtung, BGH X ZR 25/06 - Insassenschutzsystemsteuereinheit). The interpretation rule developed in the present decision (the patent seeks to delimit itself from the prior art described therein) seems therefore to be in line with prior Supreme Court case law. According to the reasoning of the present decision, this interpretation rule seems to be derived from a principle set forth in a decision of the High Court of England and Wales (RPC 1995, 705; GRUR Int. 1997, 373ff., in extracts).
The present decision was made in patent nullity proceedings. Thus, a claim interpretation, applying the principles developed in the present decision, might be possibly in favour of the patent owner. A narrower interpretation of the claimed subject matter might lead to a delimitation from the state of the art cited by an opponent. At the same time, it is logical that that the interpretation rule employed in the present decision might be applicable to claim interpretation in infringement proceedings. In the worst case scenario for a patent owner, applying the interpretation principles employed in the present decision could lead to a narrower scope of protection and even exclude infringing matter. Admittedly, the foregoing scenarios are extreme ones. Moreover, the interpretation rule is only applicable when there is doubt. It is therefore unlikely to be sensible to draw general conclusions from this decision about the extent of acknowledging prior art when drafting a patent application or during the examination proceedings, since it is impossible to predict if one of the aforementioned scenarios will occur.
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