A court in Japan has ruled that an 88-year-old former boxer sentenced to death in 1968 on a wrongful murder conviction is innocent.

The Shizuoka District Court said on Thursday that Iwao Hakamada was not guilty in a retrial for the quadruple murder of a company manager and three of his family members in 1966.

Presiding judge Koshi Kunii said the court acknowledged multiple fabrications of evidence and that Hakamada was not the culprit, according to a report by Japanese broadcaster NHK.

Freed in 2014 pending retrial, Hakamada had languished on death row for 46 years after what turned out to be a forced confession for the murders at the miso (soy paste) factory where he had been hired in 1965.

Hakamada initially denied having murdered factory boss Fumio Hashiguchi and the latter’s wife and two teenage children and setting fire to their home but confessed following what he later described as a brutal police interrogation that included beatings.

Central to the trial was a set of blood-stained clothes found in a tank of miso a year after the 1966 murders, used as evidence to incriminate Hakamada.

The defence accused investigators of a set-up, saying that the red stains on the clothes were too bright, but prosecutors said their own experiments showed the colour was credible.

Despite his death sentence, Hakamada was not executed due to lengthy appeals and the retrial process.

He was granted temporary release in 2014 after new DNA evidence cast serious doubt on the reliability of his conviction.

The Tokyo High Court last year granted him a retrial, which began in October.

Hakamada was not present for his retrial, but his 91-year-old sister Hideko Hakamada, who waged a long battle for her brother’s retrial, bowed deeply to the judge several times after the conviction was overturned.

Iwao Hakamada (centre) enters the Tokyo High Court in 2023, accompanied by his sister Hideko Hakamada, who fought for his retrial [File: Kazuhiro Nogi/AFP]

Japan is the only major industrialised democracy other than the United States to retain capital punishment, a policy that has broad public support.

Hakamada’s acquittal makes him the fifth death row convict to be found not guilty in a retrial in Japan’s post-war history.