The Tokyo High Court on Monday turned down a request to extradite a researcher to the United States to stand trial on industrial espionage charges, marking Japan's first rejection of an extradition request from American authorities.

Takashi Okamoto, 43, was charged in Ohio in May 2001 with stealing genetic materials on Alzheimer's disease developed by the Learner Research Institute at the Cleveland Clinic Foundation in July 1999 while he worked there as a researcher.

Okamoto, who had returned to Japan by the time of the indictment, has denied committing industrial espionage.