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Supreme Court Affirms Clear and Convincing Evidence Standard of Proof for Patent Invalidity

June 09, 2011

David M. Conca & Angela C. Ni

In a case followed closely by the patent bar, the Supreme Court today unanimously affirmed the clear and convincing evidence standard of proof for patent invalidity determinations. Microsoft Corp. v. i4i Ltd. Pship, No. 10-290 (S. Ct. June 9, 2011) (Slip op.).

In an opinion by Justice Sotomayor, the Court found in favor of patentee i4i against Microsoft, which had argued that the lesser preponderance of the evidence standard of proof should apply in patent invalidity cases. Specifically, Microsoft had argued (1) that a defendant in an infringement action need only persuade the jury of an invalidity defense by a preponderance of the evidence; and, alternatively, (2) that the preponderance standard must apply at least when an invalidity defense rests on evidence that was never considered by the Patent Office.

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