In a decision rendered late Friday, Judge Michael A. Telesca of the United States District Court for the Western District of New York ruled U.S. Patent No. 5,596,656 invalid, citing prior art that showed Xerox's "unistroke system" was not unique.

At the same time, the judge issued a summary judgment, dismissing Xerox's patent infringement suit against Milpitas, Calif.-based PalmOne. Xerox originally sued 3Com, the corporate parent of Palm. Palm later split into two companies, palmOne, which makes hardware, and PalmSource, (which provides software.

Xerox executives were not immediately available for comment.

Xerox's patent, awarded in January 1997, covers a method for the computerized recognition of handwriting that recognizes symbols as unbroken keystrokes: when the stylus lifts from the electronic tablet, a new character is assumed. The claim includes a manual pointer, a sensor mechanism, a display and a character generator.

Xerox sued 3Com, the original producer of the Palm Pilot PDA, in June 2000 for patent infringement over Graffiti, the simplified, single-keystroke characters used to input information into the device. PalmSource no longer uses Graffiti in its products.

3Com won an initial summary judgment. A federal appeals court reversed that ruling, finding that Graffiti did infringe. It then sent the case to the U.S. District Court to decide whether the patent was valid.