Former world boxing champions and other supporters filed pleas Monday that the Supreme Court order a retrial for a former boxer who has been on death row for 38 years, arguing he was wrongly convicted of killing a family of four in 1966.

The top court has been looking into a retrial request on behalf of Iwao Hakamada, 70, who was convicted of killing an executive with a miso maker, the man's wife and their two children.

The supporters presented the top court with some 500 letters from across Japan asking it to order a retrial. Among those who wrote the letters were former world junior middleweight champion Koichi Wajima, 63, and former world junior flyweight champion Katsuo Tokashiki, 46.

Wajima heads a committee of the East Japan Boxing Associations in support of Hakamada.

Hakamada's sister, Hideko, 73, told a news conference she is encouraged by the support from Japan's pro boxing community. She said she is "worried most about her brother's health."

Wajima told the news conference, "Hakamada is innocent."

Hakamada has refused to speak with his lawyers since March 2003.