TOKYO : A man believed to be the world's longest-serving death row inmate walked free from jail Thursday after decades in solitary confinement, in a rare about-face for Japan's rigid justice system.A slightly unsteady-looking Iwao Hakamada, 78, emerged from the Tokyo prison with his campaigning sister after Shizuoka District Court in central Japan ordered a fresh trial over the grisly 1966 murder of his boss and the man's family. Presiding judge Hiroaki Murayama said he was concerned that investigators could have planted evidence to win a conviction almost half a century ago as they sought to bring closure to a crime that had shocked the country."There is a possibility that key pieces of evidence have been fabricated by investigative bodies," Murayama said in his ruling. Shizuoka prosecutors, who have three days to appeal the decision, told Japanese media that the court's decision was "unexpected". 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, who say the justice system is heavily skewed in prosecutors' favour.Hakamada is the sixth person since the end of World War II to receive a retrial after having a death sentence confirmed, and his case will bolster opponents of capital punishment. Of the past five former death-row inmates who received retrials in Japan, four were subsequently cleared. Higher courts threw out a retrial motion for the fifth prisoner, although his lawyers have submitted a fresh request for a retrial with new evidence.After his arrest, Hakamada initially denied accusations that he robbed and killed his boss, the man's wife and their two children before setting their house ablaze. But the former boxer, who worked for a bean-paste maker, later confessed following what he subsequently claimed was a brutal police interrogation that included beatings. He retracted his confession, but to no avail, and the supreme court confirmed his death sentence in 1980.Prosecutors and courts had used blood-stained clothes, which only emerged a year after the crime and his arrest, as key evidence to convict Hakamada. The clothes did not fit him, his supporters said. The blood stains appeared too vivid for evidence that was discovered so long after the crime. Later DNA tests found no link between Hakamada, the clothes and the blood stains, his supporters said.But the now-frail Hakamada remained in solitary confinement on death row, regardless. His supporters and some lawyers, including the Japan Federation of Bar Associations, have loudly voiced their doubts about the evidence, the police investigations and the judicial logic that led to the conviction.