Effectively reversing Cybor Corp., which flatly stated that a lower court’s claim construction is a question of law which is to be reviewed de novo by the Fed. Cir., yesterday the Supreme Court held 7-2 that questions of fact resolved by a district court prior to claim construction must be given deference by the Fed. Cir. and only reversed if clearly erroneous.

The basic dispute arose over whether or not the term “molecular weight” was adequately defined — it could be calculated three different ways — or if the information in the specification, including a graph showing the peak average molecular weight met the requirements of s. 112(2). The experts disputed a discrepancy between value shown on the graph’s legend and the value at the actual peak of the curve. Teva’s expert testified that difference was small and was due to the conversion of the data from a chromatogram to the m.w. distribution curve in the figure. The District Court agreed, but the Fed. Cir. rejected these factual findings, without explaining why it was “clearly erroneous.” The Supreme Court vacated the Fed. Cir’s. Judgment of s. 112(2) invalidity and remanded, thus endorsing a “clear error” and not a de novo standard for review.

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