The U.S. government is backing i4i in its case against Microsoft that the Supreme Court is expected to hear in April.
Acting Solicitor General Neal Kumar Katyal filed an amicus brief supporting a U.S. Court of Appeal decision and i4i's position on Friday. The brief represents the U.S. Patent and Trademark Office.
i4i sued Microsoft for patent infringement over an XML-editing feature in Word. The Canadian software developer was awarded $290 million in damages and Microsoft was ordered to make changes to Word.
Other large companies have also filed amicus briefs supporting i4i, including DuPont, 3M, Johnson & Johnson, Procter & Gamble and General Electric.
Microsoft has appealed the case to the nation's highest court. Several large corporations sided with Microsoft in amicus briefs, including Google, Apple, Wal-Mart and Toyota.
Microsoft is arguing that a different standard of evidence should have been used in determining whether it had infringed on i4i's patent. The Texas jury in the U.S. District Court ruled on the basis of a "preponderance of evidence" rather than the higher standard of proof, "clear and convincing evidence."