Supreme Court of the United States
Decided: June 9, 2011


The Supreme Court unanimously affirmed the Federal Circuit’s judgment by upholding a clear and convincing standard for proving a patent invalid under 35 U.S.C. § 282, whether or not the evidence had been considered by the patent examiner. The majority opinion, which is the holding of the Court, is summarized below. The Court’s opinions may be accessed at

Brief Background

In asserting patent invalidity as a defense to an infringement action, an alleged infringer must contend with §282 of the Patent Act of 1952 (Act), under which “[a] patent shall be presumed valid” and “[t]he burden of establishing invalidity . . . shall rest on the party asserting” it. Since 1984, the Federal Circuit has read §282 to require a defendant seeking to overcome the presumption to persuade the factfinder of its invalidity defense by clear and convincing evidence. Microsoft’s argued that to succeed with a defense of patent invalidity, a mere preponderance of the evidence should be sufficient.

Brief Analysis

Citing the plain meaning of §282 and the Supreme Court’s own precedent, the Court rejected Microsoft’s contention that a defendant need only persuade the jury of a patent invalidity defense by a preponderance of the evidence. The Court noted that while §282 includes no express articulation of the standard of proof, where Congress uses a common-law term in a statute, the Court assumes the term comes with a common law meaning. Here, by stating that a patent is “presumed valid,” Congress used a term with a settled common-law meaning. According to its settled meaning, a defendant raising an invalidity defense bears a heavy burden of persuasion requiring proof of the defense by clear and convincing evidence. Furthermore, in its precedential opinion, RCA v. Radio Engineering Laboratories, Inc., 293 U.S. 1, the Supreme Court stated that “there is a presumption of [patent] validity [that is] not to be overthrown except by clear and cogent evidence.”

The Court also rejected Microsoft’s argument that a preponderance standard must at least apply where the evidence before the factfinder was not before the PTO during the examination process. While acknowledging that the rationale underlying the presumption that the PTO has approved the claim seems diminished, the Court reasoned that Congress codified the common-law presumption of patent validity and, implicitly, the heightened standard of proof attached to it. According to the Court, nothing in §282’s text suggests that Congress meant to depart from that understanding to enact a standard of proof that would rise and fall with the facts of each case. The Court stated that had Congress intended to drop the heightened standard of proof where the evidence before the jury varied from that before the PTO, it presumably would have said so expressly.