A man believed to be the world’s longest-serving death row inmate, who walked free from jail on Thursday after decades in solitary confinement, will require hospital treatment for about six months, his sister said Saturday.

An unsteady-looking Iwao Hakamada, 78, emerged from the Tokyo prison with his campaigning sister after Shizuoka District Court ordered a fresh trial over the grisly 1966 murder of his boss and the man’s family.

On Friday, he underwent a medical check-up, but his sister Hideko, 81, said the years of confinement had left her brother mentally and physically unstable, TBS reported. She said he was having trouble making conversation and simple decisions.

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 Hakamada remained in solitary confinement on death row, regardless.

© Japan Today/AFP