Human rights group Amnesty International says Japan's use of capital punishment is "shrouded in secrecy" and has criticised its treatment of death row prisoners who are kept in solitary confinement for years.
Launching its annual review on Thursday of the death penalty around the world, Amnesty said the United Nation's Committee Against Torture has signalled its concerns about the Japanese criminal justice system.
The report came as a Japanese court granted a retrial to a death-row inmate who has been confined since 1966 for a quadruple murder, decades after doubts emerged about his guilt and as the judge said key evidence may have been planted.
"The use of the death penalty in Japan continued to be shrouded in secrecy," Amnesty said in its latest report, which showed the world's largest economy executed eight people in 2013. The tally was ninth largest, the group said.
China topped the list but Amnesty said it was difficult to know the full extent of the practice there.
The organisation said it could not confirm reliable figures for Malaysia or North Korea.
Japan and the United States are the only major industrialised democracies to carry out capital punishment, a practice that has led to repeated protests from European governments and human rights groups.
International advocacy groups say the Japanese system is cruel because death row inmates can wait for their executions for many years in solitary confinement and are only told of their impending death a few hours ahead of time.
Japan executes elderly inmates and those who are preparing to apply for retrials "in contravention of international standards on the use of the death penalty," Amnesty said.
The UN commission has pointed to the "unnecessary secrecy and uncertainty surrounding the execution of prisoners; the use of solitary confinement for prisoners sentenced to death, some exceeding 30 years," Amnesty said.
The report came as Shizuoka District Court decided to "start the retrial over the case" of Iwao Hakamada, 78, who was convicted for the grisly murder of his boss and the man's family nearly five decades ago.
