The Tokyo High Court on Friday dismissed the appeal of former Sumitomo Corp. chief copper trader Yasuo Hamanaka, upholding a lower court ruling in March 1998 that sentenced him to eight years in prison for fraud and forgery.

Hamanaka, 51, had been found guilty of defrauding Sumitomo's Hong Kong subsidiary of $770 million and forging the signatures of his former bosses to conceal his off-the-book trading, causing $2.6 billion in losses to the trading giant.

The presiding judge, Tomoo Araki, said the defendant "took advantage of the full trust" held in him by the Hong Kong subsidiary, rejecting an argument by defense lawyers that the subsidiary's poor risk management should be considered.