Pair acquitted of murder after 20-year in jail

This combo shows a photo of Keiko Aoki and a photo of her common-law husband Tatsuhiro Boku during their press conference in Osaka on August 10, 2016 (AFP)

A Japanese woman and her former partner were acquitted Wednesday in a retrial for the alleged murder of the woman's 11-year-old daughter after the pair had spent about two decades in jail.

They were released in October last year after a new trial was ordered due to serious questions about their guilt -- including the validity of their confessions -- in the arson murder for which they had been convicted.

And on Wednesday the Osaka District Court formally found Keiko Aoki and Tatsuhiro Boku not guilty, a member of their support group told AFP.

The couple had been found guilty of setting their house on fire by spraying gasoline in the garage -- a blaze that killed Aoki's daughter Megumi -- in an attempt to claim insurance money.

In the ruling, the court said that confessions made by Aoki and Boku when under investigation were invalid, according to the supporter, who asked not to be named.

Details of the acquital were included on the support group's website and were widely reported by major Japanese media.

"There is a possibility that the two were forced into making false confessions after (investigators) instilled fear in them and applied excessive psychological pressure," presiding Judge Goichi Nishino said, according to Kyodo News agency.

The court also ruled it was possible the fire was an accident.

The acquittal comes after Iwao Hakamada -- believed to be the world's longest-serving death row inmate -- walked free from jail in 2014 following decades in solitary confinement, in a rare about-face for Japan's rigid justice system.

He had been accused of being responsible for the grisly 1966 murder of his boss and the man's family, but doubts arose about the reliability of his confession.