Yasuo Hamanaka, a former chief copper trader at Sumitomo Corp., was sentenced to eight years in prison March 26 for fraud and forgery that eventually cost the trading giant some $2.6 billion -- the largest trading loss ever.

The Tokyo District Court found Hamanaka, 50, guilty of defrauding Sumitomo's Hong Kong subsidiary out of $770 million and forging the signatures of his former bosses to conceal his off-the-book trading.

The court also blamed the trading company for failing to properly supervise Hamanaka's trading and for poor crisis management, which it said allowed the losses to snowball. Hamanaka, once an influential dealer known as "Mr. Five Percent" because he was said to control 5 percent of the global copper market, stood motionless as presiding Judge Yoshifumi Asayama handed down the sentence. He then blinked hard and swallowed as if to calm himself. Prosecutors had demanded a 10-year sentence.