The Enlarged Board of Appeal of the European Patent Office (EPO) recently issued much awaited decisions (G1/03, G2/03) concerning the use of disclaimers to delimit the claimed subject matter of a patent. Pragmatically, the Enlarged Board has decided that the use of a disclaimer without basis in the original application does not constitute prohibited added subject matter.

It had long been accepted EPO practice to allow amendment of an application after filing in order to acknowledge relevant prior art. This acknowledgement was thus an explicit or implicit disclaimer of that cited art. It had also become widely accepted that explicit disclaimers in the claims could be used to delimit the scope against so called "accidental anticipations". These disclaimers were typically used in the chemical fields, for example where a claim covering a broad range of substances or parameters was anticipated by a single instance of a known product falling within the range but nevertheless irrelevant to the problem addressed by the invention. In such cases, the claim would be rendered novel by explicitly excluding the known instance. It had also been good law that such a disclaimer could not serve to overcome any deficiency with respect to inventive step.

The accepted practice was overturned by the finding in T323/97 that such introduction of a disclaimer effectively added subject matter to the application beyond that which was originally disclosed. The EPO has always taken a strict - some would say pedantic - line on the addition of subject-matter. In T323/97 it was made clear that the prohibition of added matter took precedence over the need to distinguish prior art. 3 The Enlarged Board is not formally a further instance of appeal. It may be referred questions of law when technical or legal Boards of Appeal have reached divergent decisions in similar cases. The Enlarged Board may also be requested by the President of the EPO to harmonise a point of law. In the present case, the referral was based on diverging decisions and additionally on the referral of a further question by the EPO President. In the meantime, examination of all cases involving the issue of disclaimers was stayed.

The decisions in G1/03 and G2/03 pragmatically conclude that a disclaimer to avoid an accidental anticipation or to prevent double patenting of "interfering applications" does not necessarily constitute added matter. The Board goes on to provide guidelines concerning the conditions that must be fulfilled by such disclaimers and also touches on an aspect referred by the EPO President, namely the use of disclaimers to remove subject matter excluded for "non-technical reasons" (e.g. claims covering human animals or medical methods).

The underlying point of law is very significant as, had the decisions gone the other way, they would have likely opened up a flood of revocation actions. Cases that had used disclaimers to confer novelty would otherwise have been held to contain added matter which could not have been remedied without further invalidating the patent.

While this means that the established use of disclaimers can now resume with added certainty, it will be interesting to see how far the decisions will be stretched in other new directions!

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