Tokyo's High Court on Monday ordered a retrial for former boxer Iwao Hakamada, who became known as the longest-serving death row inmate in the world.

The 87-year-old was convicted of murder in 1968. He is believed to be the world's longest-serving death row inmate.

Hakamada spent nearly five decades on death row before a lower court ordered a retrial and freed him while his case proceeded.

He was handed a death sentence for robbing and murdering his boss, the man's wife and their two teenage children.

Hakamada initially denied the allegations and later presented a confession to police. But the former boxer claims that this followed a brutal interrogation that included beatings.

According to the Japan Times daily, interrogations lasted for an average of 12 hours each day. In Japan, suspects are not permitted to have a lawyer present during interrogations.

Following the sentence, Hakamada attempted to retract his confession, but it was confirmed in 1980.

Why has a retrial been ordered in Hakamada's case?

In 2014, a district court in the central city of Shizuoka found that investigators could have planted evidence and granted a retrial.

Tokyo's High Court overturned the lower court ruling in 2016. Four years later, the country's Supreme Court ruled that the High Court must reconsider its decision.

One key piece of evidence used to convict Hakamada was a set of blood-stained clothes found in a miso barrel more than a year after the murder and robbery.

According to the Japan Times, the defense team has argued they must have been planted, as they would have been discolored after being in a miso barrel for more than a year.

The NHK broadcaster said the court's presiding judge cast doubt on the evidence's credibility.

"There is no evidence other than the clothes that could determine Hakamada was the perpetrator, so it is clear that reasonable doubt arises," he said.

Reactions

Lawyers for Iwao Hakamada unfurled banners reading "retrial," while supporters shouted "Free Hakamada now!"

Hideko Hakamada, who is the former boxer's sister, said: "I was waiting for this day for 57 years and it has come."

"Finally a weight has been lifted from my shoulders."

Hideaki Nakagawa, Director of Amnesty International Japan, called the ruling a "long-overdue chance to deliver some justice to Hakamada Iwao."

Nakagawa said that Hakamada spent "more than half a century under sentence of death despite the blatant unfairness of the trial that saw him convicted."

This report was written in part with material from Agence France-Presse.

Edited by: Richard Connor