Death row inmate Iwao Hakamada (L), flanked by his sister Hideko, is released from Tokyo Detention House in Tokyo, in this photo taken by Kyodo March 27, 2014. [Photo/Agencies]

TOKYO - The world's longest-serving death row inmate was freed Thursday by a Japanese court which found investigators had likely fabricated evidence in the murder case that put the former pro boxer behind bars for nearly half a century.

The Shizuoka District Court suspended the death sentence and ordered a retrial for 78-year-old Iwao Hakamada, who had been convicted in the 1966 murder of a family and was sentenced to death in 1968. More than 45 of his 48 years in prison have been on death row, making Hakamada the longest-serving such inmate, according to Guinness World Records.

Hours later, Hakamada walked out of the Tokyo Detention Center, escorted by his sister as dozens of journalists and supporters waited outside. Hakamada looked briefly at the crowd and got inside a car without speaking.

Hakamada was not executed because of a lengthy appeals process. It took 27 years for the Supreme Court to deny his first appeal for a retrial. He filed a second appeal in 2008, and the court finally ruled in his favor on Thursday.

"It is unbearably unjust to prolong detention of the defendant any further," presiding Judge Hiroaki Murayama said in a statement. "The possibility of his innocence has become clear to a respectable degree."

Hakamada was convicted of killing a company manager and his family and setting fire to their central Japan home, where he was a live-in employee.

The court said Thursday that a DNA analysis obtained by Hakamada's lawyers suggested that investigators had fabricated evidence. Blood stains detected on five pieces of clothing, which investigators said were worn by the culprit during the crime, did not match the DNA of Hakamada, and trousers that prosecutors submitted as evidence were too small for Hakamada and did not fit when he tried them on.

Shizuoka District deputy chief prosecutor Takashi Nishitani said the ruling was unanticipated and that prosecutors would discuss whether to appeal.