As we have previously noted (here, for example), whatever else you may want to say about the folks at Microsoft, they certainly are not quitters. Now, their perseverance has raised an issue which is of paramount importance to all patent owners, but which has gone largely unnoticed – until now.

An increasingly common tactic among those accused of patent infringement is to seek re-examination of the subject patent or patents. This may occur even while litigation is proceeding in a district court, leading to the possibility that a jury finds the patent valid and infringed while the Patent Office, shortly thereafter, finds the same patent invalid. What happens then? (Flexiteek Americas, Inc. et al. v. Plasteak, Inc. et al.)

A recent decision of the United States District Court for the District of Delaware (In Re: `318 Patent Infringement Litigation) has cast new light on the tension between two sometimes conflicting requirements for patent validity: “nonobviousness” and “enablement.”

In order to be valid, a patent must claim subject matter that, as a whole, would not have been obvious, at the time the invention was made, to a person having ordinary skill in the art to which the subject matter pertains.¹