The "on-sale" defense

What happens when a company starts to explore selling an invention before a U.S. patent application has been filed? That was the question before the Court of Appeals for the Federal Circuit (CAFC) in the recent case of Group One v. Hallmark. The court rejected Hallmark's "on-sale" defense and held that Group One's patents were not invalid for violating the grace period. It thus sent the case back to the district court for a full trial of Group One's charge of infringement.