Yet again we have acquittals of people falsely charged and convicted based on wrongful confessions coerced by investigators. In this case, a 52-year-old Osaka woman and her former partner spent 20 years behind bars for arson and the murder of her 11-year-old daughter in 1995, until their retrial plea filed in 2009 was eventually endorsed last year and led to their release. The decision Wednesday by the Osaka District Court finding Keiko Aoki and Tatsuhiro Boku innocent must be followed up by a thorough examination by both the investigation authorities and the judiciary to find out why the prosecution’s case against the pair — based almost entirely on confessions made during interrogation that were retracted in court — went unchallenged.

The prosecution’s case held that Aoki and Boku, arrested shortly after the July 1995 death of the girl in a fire at their home in Osaka, had conspired to kill her for the benefits from a life insurance scheme taken out on the victim — that Aoki made her daughter take a bath, and then Boku sprayed gasoline in the garage next to the bathroom and set it on fire with a lighter. In the absence of material evidence, the key to the case was a confession that Boku allegedly made to interrogators detailing how he set the garage on fire, along with a statement by Aoki acknowledging her own complicity. Even though they pleaded innocent throughout their trials, the Osaka District Court in 1999 handed down a life term for both — a decision endorsed by the Osaka High Court in 2004 and finalized by the Supreme Court in 2006.

Their 2009 retrial plea was approved by the Osaka District Court in 2012, a decision challenged by prosecutors but endorsed in October 2015 by the Osaka High Court, which ordered that their prison terms be suspended and they be freed. What proved key to reopening the case was a test performed by their lawyers — and later by the prosecution themselves — to re-enact the scene of the alleged arson based on the account that Boku gave to investigators. The result — in both the defense and prosecution tests — clearly contradicted what he said during interrogation, thus putting the credibility of his confession in doubt. The defense test instead pointed to the possibility — also endorsed in the district court decision this week — that the fire was caused accidentally by gasoline leaking from the tank of a vehicle in the garage that was set alight by the pilot light of the bathtub water heater.

Furthermore, police investigation reports and notes kept by investigators — disclosed as evidence in the retrial process — showed that the officers who questioned the two used coercive and deceitful tactics to get them to confess, during which they both wavered between confessing to and denying the charges. In its acquittal of Aoki and Boku, the district court rejected the credibility of their confessions as evidence, saying it is suspected that the police investigators put the two in a “situation where they had no choice but to make false confessions” by “instilling fear and adding excessive psychological pressure” from the time they were arrested.

The question that needs answering is why all these obvious doubts were not raised during their initial trials — or even during the police investigation and the subsequent probe by prosecutors. This is the question that all parties involved in the criminal justice system must address. Wednesday’s ruling exposed how police investigators led the suspects into confessing to acts they had not committed, but does not reflect on how the judiciary itself failed to challenge the investigators’ version of events.

Wrongful convictions have often been reversed on the introduction of new evidence — either that which had been previously withheld by prosecutors or that made available with technological advances, such as more precise DNA tests. But the fact that a test to re-enact the scene of this fire was performed only after the two had been convicted and spent years in prison points to negligence on the part of the investigators, who relied on confessions to build their case and then failed to verify them on scientific grounds.

Interrogation by investigators behind closed doors — which makes it difficult to objectively determine whether the suspects made their statements voluntarily — has long been blamed as a source for wrongful confessions, and the false convictions based largely on such confessions. The tendency remains for investigators to rely on confessions to build their cases when they lack material evidence. In the face of public criticism, the police and prosecutors have gradually introduced electronic recording of their interrogations to make the process more transparent. An amendment to the Criminal Investigation Procedure Law enacted in May made video-recording of the entire interrogation process mandatory — but that rule will apply only to criminal cases handled by lay judge trials and those exposed by prosecutors’ independent probes — which together account for about 3 percent of all criminal cases — and investigators will have the discretion to bypass electronic recording if they judge it will make it difficult for them to obtain meaningful confessions.

We need to seek out the lessons from the acquittals of Aoki and Boku to determine whether the criminal justice reforms that have been implemented are enough to eliminate the risk of wrongful convictions.

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