LeapFrog sued Mattel in October 2003, claiming its PowerTouch toy infringed a patent related to the LeapPad electronic books range. An appeals court in Washington upheld a March 2006 decision by a US District Court that LeapFrog's patent was invalid and not infringed.
"LeapFrog comes well short of supporting a definite and firm conviction that a mistake has been made," the US Court of Appeals for the Federal Circuit said in a ruling posted on its Web site. The court specialises in patent cases.
Fisher-Price's toy uses different technology from that covered by the patent, according to the ruling of the appeals panel.
The appeals court agreed with Fisher-Price that LeapFrog's invention was nothing more than "a toy that teaches reading based on the association of letters with their phonemic sounds, updated with modern electronics" and was thus an obvious variation of earlier toys.
LeapFrog claimed Fisher-Price copied the technology from LeapPad books that lets children press the letters of a word to hear how they sound. LeapFrog began selling LeapPad books in 1999 while Mattel introduced PowerTouch in 2003.