The Nagoya District Public Prosecutor's Office on Tuesday indicted a deputy chief guard at Nagoya Prison on charges of assault resulting in the death of a male inmate in 2001.
Mikio Otomaru, 46, is the seventh officer at the prison to be indicted for allegedly abusing prisoners.
The six others were indicted last year on charges of inflicting serious injuries in May and September on two other inmates, one of whom died.
According to the indictment, Otomaru aimed water from a high-pressure fire hose at the 43-year-old inmate's bare buttocks Dec. 14, 2001. The attack, which took place in a prison cell, was apparently aimed at punishing the inmate for unruly behavior.