A court decision last week to reopen a 1985 murder trial in Kumamoto Prefecture makes yet another case for requiring prosecutors to disclose all evidence in criminal trials, given the risk that selective use of evidence by investigation authorities can result in wrongful convictions. Koki Miyata, now 83, served 13 years in prison. He is only the latest among people whose guilt for crimes was thrown in doubt by a piece of evidence withheld by the prosecution until after they were convicted and only made open in the process of reopening their cases.

In the absence of material evidence that he killed a man in January 1985, the key to Miyata's conviction was the confession he made to interrogators. Though he withdrew his confession halfway through the trial and pleaded innocent, the Kumamoto District Court in 1986 gave him 13 years in prison, judging that his confession was voluntary and credible — a decision finalized by the Supreme Court in 1990.

What led the same district court to decide last week to grant Miyata a retrial was new evidence, including an item that contradicted his own statement to the interrogators. Miyata had initially confessed that he tore off a part of his own shirt, wrapped the cloth around a knife that he used to stab the victim so that the weapon would not be blood-stained, and burned the strip of cloth after the crime. Years after he was convicted, however, his lawyers found that the pieces of cloth that made up his whole shirt were intact and in the possession of the prosecutors, who had not submitted them as evidence in his trial.