The U.S. Supreme Court issued its decision in Microsoft v. i4i (PDF) and held in favour of i4i, upholding the “clear and convincing evidence” standard of evidence needed overcome the presumption of validity in an issued patent.Microsoft was appealing a lower court decision that had found that it had infringed Toronto-based i4i’s patent relating to code in Microsoft Word. Microsoft had argued that only a preponderance of evidence was required to invalid a patent. The Court also rejected Microsoft’s argument that the standard of evidence be lower for evidence that was not before the patent office during prosecution.

The introduction from the decision summarizes the holding of the court:

Under §282 of the Patent Act of 1952, “[a] patent shall be presumed valid” and “[t]he burden of establishing in-validity of a patent or any claim thereof shall rest on the party asserting such invalidity.” 35 U. S. C. §282. We consider whether §282 requires an invalidity defense to be proved by clear and convincing evidence. We hold that it does.

Articles and commentary on the case are available at Patently-O, and the Globe and Mail.

Update June, 15: My summary of this case was posted on the Dimock Stratton website.