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Case Basics
Docket No. 
Microsoft Corporation
I4I Limited Partnership, et al.
Decided By 
(for the petitioner)
(for the respondents)
(Deputy Solicitor General, Department of Justice, for the United States as amicus curiae, supporting the respondents)
Facts of the Case 

The owner of a patent for a computer language, i4i Limited Partnership brought suit against Microsoft Corp., alleging that the custom XML editor in certain versions of Microsoft Word, Microsoft's word-processing software, infringed i4i's patent. The jury found Microsoft liable for willful infringement, rejecting the company's argument that the patent was invalid, and awarded $200 million in damages to i4i.

The U.S. District Court for the Eastern District of Texas denied Microsoft's motions for a new trial. And the U.S. Court of Appeals for the Federal Circuit upheld the district court order, finding that Microsoft needed to offer "clear and convincing evidence" to overcome the traditional presumption that patents approved by the U.S. Patent and Trademark Office are valid.


Must a challenge to a patent's validity offer clear and convincing evidence as proof

Decision: 9 votes for i4i Limited Partnership, 0 vote(s) against
Legal provision: Patent invalidity

Yes. The Supreme Court affirmed the lower court order in a unanimous opinion by Justice Sonia Sotomayor. "Section 282 requires an invalidity defense to be proved by clear and convincing evidence," Sotomayor wrote. Justice Stephen Breyer wrote a concurring opinion joined by Justices Antonin Scalia and Samuel Alito, in which he "join[s] the Court's opinion in full" but added that "I write separately because, given the technical but important nature of the invalidity question, I believe it worth emphasizing that in this area of law as in others the evidentiary standard of proof applies to questions of fact and not to questions of law."

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MICROSOFT v. I4I LIMITED PARTNERSHIP. The Oyez Project at IIT Chicago-Kent College of Law. 02 September 2015. <>.
MICROSOFT v. I4I LIMITED PARTNERSHIP, The Oyez Project at IIT Chicago-Kent College of Law, (last visited September 2, 2015).
"MICROSOFT v. I4I LIMITED PARTNERSHIP," The Oyez Project at IIT Chicago-Kent College of Law, accessed September 2, 2015,