[JURIST] The US Supreme Court [official website; JURIST news archive] unanimously ruled [opinion, PDF] against Microsoft [corporate website] Thursday in Microsoft v. i4i Limited Partnership [docket], holding that a patent will be invalidated only if the challenging party meets the “clear and convincing evidence” standard. The Supreme Court affirmed a US Court of Appeals for the Federal Circuit [official website] ruling, which held [opinion, PDF; JURIST report] that a challenger to a patent claim must prove invalidity by clear and convincing evidence. In 2007, i4i [corporate website] claimed that Microsoft’s products infringed i4i’s patent, which “claims an improved method for editing computer documents, which stores a document’s content separately from the metacodes associated with the document’s structure.” § 282 of the Patent Act of 1952 [35 USC §§ 1–376 text] declares that “[a] patent shall be presumed valid” and “[t]he burden of establishing invalidity of a patent or any claim thereof shall rest on the party asserting such invalidity.” Microsoft claimed it needed to prove the patent invalid by a preponderance of the evidence. Justice Sotomoyor, writing for the court, said that common law precedent established a higher burden for patent challengers:

[B]y the time Congress enacted §282 and declared that a patent is “presumed valid,” the presumption of patent validity had long been a fixture of the common law. According to its settled meaning, a defendant raising an invalidity defense bore “a heavy burden of persuasion,” requiring proof of the defense by clear and convincing evidence.

Accordingly, she wrote, Congress adopted that high standard when it enacted the Patent Act in 1952, even though the Act does not expressly mention the burden of proof. Chief Justice John Roberts did not take part in the consideration or decision.

Justice Stephen Breyer, joined by Justice Antonin Scalia and Justice Samuel Alito, filed a concurring opinion emphasizing that the “clear and convincing evidence” standard of proof applies to fact finding, and not to finding questions of law. Justice Clarence Thomas also wrote a concurring opinion disagreeing with the majority’s assertion that Congress codified a standard of proof within the language of the Patent Act. In other words, though Congress stated “a patent shall be presumed valid,” it did not necessarily mean to attach the “clear and convincing evidence” standard typically associated with such language.