Microsoft faces a trial over patent infringement charges related to its ergonomic keyboards after a federal appeals court reversed a lower court's decision invalidating those patents yesterday.

TypeRight Keyboard sued Microsoft in July 1998, claiming that Microsoft's ergonomic keyboards violated its patents. The Microsoft Natural keyboards feature V-shaped designs with keys in separate clusters for the left and right hands and have a large wrist rest.

TypeRight asked the District Court for the Southern District of California to stop worldwide sales of the Microsoft Natural keyboard and for millions of dollars in damages, according to information from Fish & Richardson, the law firm that represented Microsoft in the matter.

Microsoft in June 2000 won a motion to invalidate the patents. The company argued that the concept of ergonomic keyboards predated TypeRight's patents. Evidence that was presented consisted of an undated document from a German company, Marquardt and testimony from paid fact witnesses.

The Court of Appeals for the Federal Circuit, in Washington, DC Tuesday ruled that there are "genuine issues" with the credibility of Microsoft's witnesses.

"While this is a close case, we conclude that summary judgement of invalidity was improperly granted and a trial is necessary to determine whether the testimony offered by Microsoft to prove that the Marquardt document was prior art is credible," the court wrote.

The appellate court sent the case back to the district court in San Diego.

TypeRight is ready to go to trial but would like to end the case with a settlement, said the company's attorney, Matthew Herron of Meisenheimer, Herron & Steele.

"It is something that we think should be settled in a businesslike way. If not, then we're prepared to have the case decided in trial by the judge and a jury," he said.

The patents are invalid and Microsoft will prevail, company spokeswoman Stacy Drake said in a statement sent via email.

"The evidence will also ultimately show that there was no infringement of any kind, and our ergonomic keyboard technology was developed by our own engineers based on pre-existing Microsoft technology," she wrote.