Lawyers for Microsoft have slammed a verdict that awarded a Canadian developer nearly $300 million in damages and resulted in an impending ban on sales of Microsoft Word, as a "miscarriage of justice."

In a brief filed with the US Court of Appeals for the Federal Circuit, Microsoft asked the three-judge panel to overthrow a Texas court's verdict and quash the injunction that prohibits the company from selling current versions of Word 2003 and Word 2007 in the US after 10 October

The brief is the first step in a fast-track process approved last week after Microsoft appealed the May jury verdict that found the company guilty of patent infringement. Two weeks ago, US District Court Judge Leonard Davis awarded software developer i4i Inc. more than $290 million in damages and interest and blocked Microsoft from selling Word in its current form.

An oral hearing for the appeal is slated for 23 September, after i4i files its response and Microsoft is given a chance to rebut.

This week Microsoft castigated Davis' role in the trial. "This case stands as a stark example of what can happen in a patent case when a judge abdicates [his] gatekeeping functions," Microsoft said. "If the district court had been more faithful to its role as gatekeeper, it should have recognised a trial run amok and interceded to prevent a miscarriage of justice."

The 84-page brief, thick with legal citations of prior cases, continued to attack Davis' judgment during the case, saying that he failed to properly instruct the jury, awarded "enhanced" damages of $40 million, $15 million more than i4i had asked for and added the injunction against selling Word.

"This is not justice," Microsoft said. "If district courts are free to admit theories of infringement that nullify a patents claim terms, specification, prosecution history, and title; if they will allow an inventor to validate his patent by testifying without corroboration that he lied about the date of conception & then patent litigation will be reduced to a free-for-all."

Attorneys for Microsoft also argued that Davis should not have issued the injunction that bars Word sales. Citing a Supreme Court ruling from 2006 that set aside a lower court's injunction against eBay in a patent dispute over its "Buy It Now" auction feature, the lawyers said i4i had failed to present evidence that justified Davis' injunction.

In its decision, the Supreme Court said that lower courts must use a four-factor test when considering patent injunctions.

Microsoft said that i4i "utterly failed to meet [the burden of irreparable harm]" and did not "present a shred of evidence on its alleged loss of brand share." The company also argued that the damage to i4i had occurred in the past, and that i4i's software was complementary to Word, not a competitive product.

Its lawyers also complained that the injunction was unfair. "Given that i4i does not even have a stand-alone product that could compete with Word on the market, while Microsoft would lose its significant investments in creating the custom XML functionality of Word and would have to invest significant resources in redesigning it, the balance of the equities plainly favours Microsoft," the company's brief said.

Finally, Microsoft claimed that Davis overlooked the public interest, one of the four factors cited by the Supreme Court in the eBay decision. "The public interest thus favors a final - and better-tested - determination of validity before Microsoft and its distributors are forced to incur additional costs in redesigning Word, and removing the current copies of Word from the market," stated the brief.

During the trial, Microsoft said it would take five months to craft new versions of Word that omitted the offending "custom" XML feature. i4i, meanwhile, countered that it could be done much faster than that with a software patch.

i4i was not available for comment, but Tuesday, the company issued a statement from its chairman Loudon Owen. "We firmly believe that the US District Court made the right decision on the merits of the case [and] we are confident that we will prevail on the appeal," Owen said. "This is a vital case for inventors and entrepreneurial companies who, like i4i, are damaged by the willful infringement of their patents by competitors; particularly competitors as large and powerful as Microsoft."