BASF sued Johnson Matthey for infringement of a patent directed to systems for performing catalytic conversion of nitrogen oxides in an exhaust gas stream. Johnson Matthey argued, and the court agreed, that language in the asserted claims of “a material composition B effective to catalyze selective catalytic reduction (SCR) of NOx” and “a material composition A effective for catalyzing NH3 Oxidation” was indefinite functional language that rendered all asserted claims invalid. BASF appealed to the Federal Circuit
The appellate court found that the specification of the Patent described specific stoichiometric chemical reactions for the catalysts, materials that could be used for “material composition A” and “material composition B,” and various examples of how the catalyst layers could be prepared and how they performed under practical engine conditions. The court found, based on ordinary meaning and examples in the patent specification and fairly standard and well-known testing conditions, that the disputed “material composition” limitations should be construed to encompass all compositions known to those of ordinary skill in the art that perform the recited functions, to whatever degree and under whatever conditions would be viewed by a relevant skilled artisan as making the material catalysts for the claimed reactions. The CAFC further found that nothing in indefiniteness law precludes defining a particular claim term by its function and that breadth of a claim limitation should not be equated with indefiniteness.
Functional language in a patent claim does not render the claim indefinite as long as a person of ordinary skill in the art, based on knowledge possessed by that person and information contained in the specification of the patent would make that person reasonably certain as to the scope of the claim.