In determining the scope of protection of a patent, the meaning of the claims of the published patent must be considered.
In a recent judgment, the Supreme Court has ruled that third parties can always rely on statements of the applicant vis-à-vis the patent granting body in interpreting the meaning of the claims of a patent.
The patent granting body (the European Patent Office in most cases) keeps an examination file which includes correspondence between the applicant and the granting body. The file sometimes contains statements of the applicant on the basis of which it may be assumed that particular matter does or does not fall within the scope of protection of the claims. In the Netherlands, it has to date been controversial to what extent the file could be relied upon in determining the interpretation of the claims in an infringement suit before the court.
In a previous judgment (Ciba Geigy v. Oté Optics, January 13, 1995), the Supreme Court ruled that the examination file could be used in favor of the patentee only with restraint. A patentee was allowed to substantiate his argumentation in favor of a broad scope of protection by reliance on the examination file only when the meaning of the claims was still doubtful after a study of the description and the drawings.
On December 22, 2006, in the case of Dijkstra v. Saier, the Supreme Court ruled that such restraint is not required if third parties (alleged infringers) rely on the examination file to interpret the patent more strictly. The restraint was intended only to protect third parties from an unexpectedly broad interpretation. When during the examination procedure a patentee has argued that something does not fall within his protection, a third party is entitled to rely on that after grant.