Disclaimers get green light

Author: Hsu Min Chung, Chartered Patent Attorney

The Enlarged Board of Appeal has recently clarified the European Patent Office's stance on disclaimers in patent claims following two conflicting Decisions from their Technical Boards of Appeal. The Enlarged Board of Appeal's Decision has helped to lift the uncertainty surrounding the use of disclaimers and the validity of patent claims in which they have been used.

The matter is of significant importance to the fields of chemistry and biotechnology where disclaimers have most commonly been used.

What is a Disclaimer?
A disclaimer is an amendment made by the introduction of a "negative" technical feature into a claim. This has the effect of excluding an embodiment of the claimed invention from the scope of a patent. For example, if a claim relates to a generic chemical formula, a particular compound falling within the general formula can be disclaimed from the scope of the claim to ensure that the claim is novel over a prior disclosure of that compound.

The Traditional Practice
In contrast to the general rule that all amendments must find clear basis in the application as originally filed, it was possible to use disclaimers to distinguish a claimed invention from a piece of prior art even when there was no explicit disclosure of the disclaimer or the subject matter disclaimed in the original application. However, such undisclosed disclaimers could only be used in certain circumstances. Specifically, the prior art disclaimed had to be either a) an earlier European patent application that had not been published at the priority date of the claimed invention and therefore only citable for novelty (prior art under Article 54(3)EPC) or b) an "accidental" anticipation that was irrelevant to the inventive step of the invention in question. There was no consistent approach, however, for determining whether or not an anticipation was accidental.

A Departure from Tradition
In T323/97 (OJ 2002, 476), the Technical Board of Appeal concluded that the established practice on disclaimers was flawed. In the Board's view, it was only possible to determine whether an anticipation was truly accidental by considering the technical problem solved by the claimed invention in the light of the prior art. This technical problem could not be determined for certain at a single point in time because further prior art could be located at a later date, which would require the problem to be reformulated.

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