A court on rejected an appeal by a farmer who has spent 40 years on death row for the murder of his wife, his mistress and three other women who died after drinking poisoned wine in rural Japan.
The Nagoya High Court on Friday "turned down the appeal for retrial" of 86-year-old Masaru Okunishi over the killings, a court spokesman said. The request could still go to the Supreme Court.
Okunishi, who has spent much of the past four decades in solitary confinement, has consistently protested his innocence after retracting what he says was a coerced confession ahead of his original trial.
But presiding judge Yasuo Shimoyama ruled "his confession is fully credible in its essential part", according to Jiji Press news agency.
The chief judge said the defence counsel had not presented enough evidence to prove a kind of pesticide Okunishi said he had used was not the poison found in the wine, it said.
Amnesty International protested the court decision.
"The death penalty is an irreversible punishment and Mr Okunishi should be granted the opportunity for a retrial," the human rights group said in a statement, calling for his prompt release in consideration of his age and on humanitarian grounds.
Five women died and 12 others fell ill after drinking wine laced with agricultural chemicals at a community get-together in the small town of Nabari, central Japan in 1961.
Okunishi initially told police that he put the lethal chemicals into white wine in an attempt to kill both his wife and his mistress and erase their complicated love triangle.
But he later withdrew his confession and in 1964 the Tsu District Court acquitted Okunishi, citing a lack of evidence.
However, the prosecution appealed the verdict. The Nagoya High Court revoked the lower court decision and sentenced him to death in 1969 - a decision upheld by the Supreme Court in 1972.
Since then, he has become one of Japan's longest serving death row inmates, despite repeated attempts by his lawyers to get a retrial on the basis that the women all died from consuming different chemicals.
Apart from the United States, Japan is the only major industrialised democracy 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 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.