When a court declared Iwao Hakamata innocent in September, the world’s longest-serving death row inmate seemed unable to comprehend, much less savour the moment.

“I told him he was acquitted, and he was silent,” Hideko Hakamata, his 91-year-old sister, tells the BBC at her home in Hamamatsu, Japan.

“I couldn’t tell whether he understood or not.”

Hideko had been fighting for her brother’s retrial ever since he was convicted of quadruple murder in 1968.

In September 2024, at the age of 88, he was finally acquitted – ending Japan’s longest running legal saga.

Mr Hakamata’s case is remarkable. But it also shines a light on the systemic brutality underpinning Japan’s justice system, where death row inmates are only notified of their hanging a few hours in advance, and spend years unsure whether each day will be their last.

Human rights experts have long condemned such treatment as cruel and inhuman, saying it exacerbates prisoners’ risk of developing a serious mental illness.

And more than half a lifetime spent in solitary confinement, waiting to be executed for a crime he didn’t commit, took a heavy toll on Mr Hakamata.

Since being granted a retrial and released from prison in 2014, he has lived under Hideko’s close care.

When we arrive at the apartment he is on his daily outing with a volunteer group that supports the two elderly siblings. He is anxious around strangers, Hideko explains, and has been in “his own world” for years.

“Maybe it can’t be helped,” she says. “This is what happens when you are locked up and crammed in a small prison cell for more than 40 years.

“They made him live like an animal.”

A former professional boxer, Iwao Hakamata  was working at a miso processing plant when the bodies of his boss, the man’s wife and their two teenage children were found. All four had been stabbed to death.

Authorities accused Mr Hakamata of murdering the family, setting their house in Shizuoka alight and stealing 200,000 yen (£199; $556) in cash.

“We had no idea what was going on,” Hideko says of the day in 1966 when police came to arrest her brother.

The family home was searched, as well as the homes of their two elder sisters, and Mr Hakamata was taken away.

He initially denied all charges, but later gave what he came to describe as a coerced confession following beatings and interrogations that lasted up to 12 hours a day.

Two years after his arrest, Mr Hakamata was convicted of murder and arson and sentenced to death. It was when he was moved to a cell on death row that Hideko noticed a shift in his demeanour.

One prison visit in particular stands out.

“He told me, ‘there was an execution yesterday – it was a person in the next cell’,” she recalls. “He told me to take care – and from then on, he completely changed mentally and became very quiet.”

Mr Hakamata is not the only one to be damaged by life on Japan’s death row, where inmates wake each morning not knowing if it will be their last.

“Between 08:00 and 08:30 in the morning was the most critical time, because that was generally when prisoners were notified of their execution,” Menda Sakae, who spent 34 years on death row before being exonerated, wrote in a book about his experience.

“You begin to feel the most terrible anxiety, because you don’t know if they are going to stop in front of your cell. It is impossible to express how awful a feeling this was.”

James Welsh, lead author of a 2009 Amnesty International report into conditions on death row, noted that “the daily threat of imminent death is cruel, inhuman and degrading”. The report concluded that inmates were at risk of “significant mental health issues”.

Hideko could only watch as her own brother’s mental health deteriorated as the years went by.

“Once he asked me ‘Do you know who I am?’ I said, ‘Yes, I do. You are Iwao Hakamata’. ‘No,’ he said, ‘you must be here to see a different person’. And he just went back [to his cell].”

Hideko stepped up as his primary spokesperson and advocate. It wasn’t until 2014, however, that there was a breakthrough in his case.

A key piece of evidence against Mr Hakamata were red-stained clothes found in a miso tank at his workplace.

They were recovered a year and two months after the murders and the prosecution said they belonged to him. But for years Mr Hakamata’s defence team argued that the DNA recovered from the clothes did not match his – and alleged that the evidence was planted.

In 2014 they were able to persuade a judge to release him from prison and grant him a retrial.

Prolonged legal proceedings meant it took until last October for the retrial to begin. When it finally did, it was Hideko who appeared in court, pleading for her brother’s life.

Mr Hakamata’s fate hinged on the stains, and specifically how they had aged.

The prosecution had claimed the stains were reddish when the clothes were recovered – but the defence argued that blood would have turned blackish after being immersed in miso for so long.

That was enough to convince presiding judge Koshi Kunii, who declared that “the investigating authority had added blood stains and hid the items in the miso tank well after the incident took place”.

Judge Kunii further found that other evidence had been fabricated, including an investigation record, and declared Mr Hakamata innocent.

Hideko’s first reaction was to cry.

“When the judge said that the defendant is not guilty, I was elated; I was in tears,” she says. “I am not a tearful person, but my tears just flowed without stopping for about an hour.”

The court’s conclusion that evidence against Mr Hakamata was fabricated raises troubling questions.

Japan has a 99% conviction rate, and a system of so-called “hostage justice” which, according to Kanae Doi, Japan director at Human Rights Watch, “denies people arrested their rights to a presumption of innocence, a prompt and fair bail hearing, and access to counsel during questioning”.

“These abusive practices have resulted in lives and families being torn apart, as well as wrongful convictions,” Ms Doi noted in 2023.

David T Johnson, a professor of sociology at the University of Hawaii at Manoa, whose research focuses on criminal justice in Japan, has followed the Hakamata case for the last 30 years.

He said one reason it dragged on is that “critical evidence for the defence was not disclosed to them until around 2010”.

The failure was “egregious and inexcusable”, Mr Johnson told the BBC. “Judges kept kicking the case down the road, as they frequently do in response to retrial petitions (because) they are busy, and the law allows them to do so.”

Hideko says the core of the injustice was the forced confession and the coercion her brother suffered.

But Mr Johnson says false accusations don’t happen because of a single mistake. Instead, they are compounded by failings at all levels – from the police right through to the prosecutors, courts and parliament.

“Judges have the last word,” he added. “When a wrongful conviction occurs, it is, in the end, because they said so. All too often, the responsibility of judges for producing and maintaining wrongful convictions gets neglected, elided, and ignored.”

Against that backdrop, Mr Hakamata’s acquittal was a watershed – a rare moment of retrospective justice.

After declaring Mr Hakamata innocent, the judge presiding over his retrial apologised to Hideko for how long it took to achieve justice.

A short while later, Takayoshi Tsuda, chief of Shizuoka police, visited her home and bowed in front of both brother and sister.

“For the past 58 years… we caused you indescribable anxiety and burden,” Mr Tsuda said. “We are truly sorry.”

Hideko gave an unexpected reply to the police chief.

“We believe that everything that happened was our destiny,” she said. “We will not complain about anything now.”

After nearly 60 years of anxiety and heartache, Hideko has styled her home with the express intention of letting some light in. The rooms are bright and inviting, filled with pictures of her and Iwao alongside family friends and supporters.

Hideko laughs as she shares memories of her “cute” little brother as a baby, leafing through black-and-white family photos.

The youngest of six siblings, he seems to always be standing next to her.

“We were always together when we were children,” she explains. “I always knew I had to take care of my little brother.  And so, it continues.”

She walks into Mr Hakamata’s room and introduces their ginger cat, which occupies the chair he normally sits in. Then she points to pictures of him as a young professional boxer.

“He wanted to become a champion,” she says. “Then the incident happened.”

After Mr Hakamata was released in 2014, Hideko wanted to make the apartment as bright as possible, she explains. So she painted the front door pink.

“I believed that if he was in a bright room and had a cheerful life, he would naturally get well.”

It’s the first thing one notices when visiting Hideko’s apartment, this bright pink statement of hope and resilience.

It’s unclear whether it has worked – Mr Hakamata still paces back and forth for hours, just as he did for years in a jail cell the size of three single tatami mats.

But Hideko refuses to linger on the question of what their lives might have looked like if not for such an egregious miscarriage of justice.

When asked who she blames for her brother’s suffering, she replies: “no-one”.

“Complaining about what happened will get us nowhere.”

Her priority now is to keep her brother comfortable. She shaves his face, massages his head, slices apples and apricots for his breakfast each morning.

Hideko, who has spent the majority of her 91 years fighting for her brother’s freedom, says this was their fate.

“I don’t want to think about the past. I don’t know how long I’m going to live,” she says. “I just want Iwao to live a peaceful and quiet life.”

Additional reporting by Chika Nakayama