At a Glance
The Patent at Stake
i4i's patent covered a method for handling a document's content separately from its structure using 'metacodes' — a map of codes stored apart from the raw text. Microsoft Word's custom XML editing was found to work the same way, letting users manipulate structure and content independently.
The Timeline
2007
i4i sues Microsoft
i4i Limited Partnership — a small Toronto software company, not a household name — sues Microsoft in the Eastern District of Texas, alleging that the custom XML editing feature in Word 2003 and 2007 infringes its 1998 patent.
May 2009
Jury: willful infringement
An East Texas jury finds Microsoft willfully infringed and awards i4i roughly $200 million. It is one of the largest patent verdicts ever entered against Microsoft.
August 2009
Enhanced damages + an injunction
The court enhances the award to about $290 million for willfulness and interest, and enters an injunction barring Microsoft from selling versions of Word with the infringing custom-XML feature. Microsoft must strip or rework the feature.
December 2009
Federal Circuit affirms
The Court of Appeals for the Federal Circuit upholds the verdict and the injunction. Microsoft ships modified versions of Word with the custom-XML capability removed.
June 2011
Supreme Court: 8–0 for i4i
In Microsoft Corp. v. i4i Ltd. Partnership, the Supreme Court unanimously rejects Microsoft's bid to lower the bar for proving a patent invalid. A challenger must still show invalidity by 'clear and convincing evidence' — even when relying on prior art the patent office never examined.
The Outcome
A feature in Word became a Supreme Court rule for every patent.
Microsoft paid i4i roughly $290 million and removed custom XML editing from the shipping versions of Word. For most companies that would be the whole story — a big verdict and a product change. But Microsoft pushed the fight to the Supreme Court on a question far bigger than one feature: how much evidence it takes to prove an issued patent invalid.
The Court's unanimous answer — clear and convincing evidence, always — is the case's lasting legacy. It means a granted US patent carries a strong presumption of validity that a defendant must overcome with more than a coin-flip's worth of proof, and it reshaped where those fights now happen.
What It Changed
Cemented the presumption of validity
Microsoft argued that when an invalidity defense rests on prior art the USPTO never considered, the challenger should only have to prove invalidity by a 'preponderance of the evidence' — the everyday more-likely-than-not standard. The Supreme Court said no: §282 sets one standard, clear and convincing evidence, for every invalidity challenge in court. Issued patents are hard to kill, by design, and i4i made that the settled law.
Helped drive the creation of inter partes review
If beating a patent in court requires clear and convincing evidence, accused infringers needed a cheaper venue with an easier standard. Months after i4i, the America Invents Act created inter partes review at the patent office — where invalidity is judged on a preponderance of the evidence. The contrast i4i sharpened is exactly why IPR became the defendant's tool of choice.
Proved a small company can move a giant
i4i had a few dozen employees. It forced the world's largest software company to pay $290 million and re-engineer its flagship product mid-cycle. The case is a touchstone for the argument that the patent system, whatever its flaws, can still let a small inventor hold a giant to account.
From PatentBrief
How do you actually invalidate a patent? →
i4i set the bar. See what a patent must clear to be valid in the first place — and where that fight happens now.