A U.S. judge in charge of Apple’s patent lawsuit against Samsung Electronics believes that Apple’s patent on its iPad tablet is invalid.

U.S. digital content magazine “paidContent.org” on Friday reported that after the preliminary injunction hearing on October 13th, U.S. District Judge Lucy Koh said that she thinks the Knight-Ridder tablet prototype from 1994 invalidates Apple’s patent on iPad.

According to the article, Christopher Carani, the chair of the American Bar Association’s Design Rights Committee, said that Koh made the reference and comment after an episode in court where she waved the Apple iPad and Samsung Galaxy tablets in the air, asking if anyone can tell the difference between the two from afar.

The Knight-Ridder tablet, similar in design to the iPad, is a device in which many of its elements are embodied in Apple’s later D’889 patent application.