On appeal, BASF argued that the "composition...effective to catalyze" has a plain and ordinary meaning and it is not indefinite because a person of ordinary skill in the art would understand it to be "composition capable of catalyzing" based on the specification. Johnson Matthey argued that the "effective to catalyze" is indefinite because the language is functional and there are limitless number of materials that can catalyze ammonia oxidation or SCR reactions.
In reversing the district court's judgment, the Federal Circuit reasoned that the Nautilus standard of "reasonable certainty" does not preclude defining a claim term by its function, that the specification provides exemplary material compositions that are effective to catalyze, and that objective tests to determine the effectiveness of the catalysts were available and well known at the time. Based on the intrinsic and extrinsic evidence, the Federal Circuit held that the claims of the asserted patent were not indefinite.