Dozens of companies and groups have filed amicus curiae briefs in support of i4i, among them large pharmaceutical corporations, universities and venture capital firms.
The case, which began in 2007 when i4i sued Microsoft in a Texas federal court, could relax the burden of proof currently on the alleged infringer, said Chang. Under current practice, an accused infringer must show "clear and convincing evidence" that the patent is invalid.
Microsoft has suggested that the burden of proof should instead be lowered to "a preponderance of the evidence."
If the Court rules for Microsoft, said Chang, "it would immediately make it easier to challenge the validity of a patent."
Microsoft has argued that i4i should not have been granted its patent because it was selling software that relied on the technology before it applied to the U.S. Patent and Trademark Office.
That prompted Associate Justice Antonin Scalia to question Microsoft's counsel today.
"Are you going to argue for all the time, in which case, you can appeal to the general rule that we always apply, or are you going to say, oh, yes, we won't apply it normally but only when the prior art hadn't been considered?" Scalia asked Thomas Hungar of the Washington D.C. law firm Gibson, Dunn & Crutcher, who represented Microsoft. "I mean, you -- you can't ride both horses. They're going in different directions," said Scalia.
i4i's lawsuit originally attracted interest because of an injunction issued in 2009 that was to bar Microsoft from selling its popular Word software. The injunction was suspended after Microsoft threatened that sales chaos would result, and several major computer makers, including Hewlett-Packard and Dell, stepped forward to say the same.
An appeals court agreed, and gave Microsoft five months to modify Word. In January 2010, the company shipped an update to Word 2007 that removed the custom XML tagging technology i4i asserted was covered by its patent.
Microsoft was also told to pay i4i nearly $300 million in damages and interest.
"We're confident that we'll win because we've had a consistent stream of successes," i4i's Owen said today as he ticked off the original ruling in U.S. District Court, and an appeal it won later.
While some observers have characterized the legal battle as one between technology Davids and Goliaths, neither Chang or Owen bought into that today.
"Originally it was a David and Goliath case, but now it's David plus a bunch of Goliaths," said Owen.
"This is a battle between the industry and a small, narrowly-defined group of opponents that have a lot of money, don't believe in patents and have a large market share that they want to protect," Owen said.
Sign up for MIS Asia eNewsletters.