The only individuals indicted over the accident at the crippled Fukushima No. 1 nuclear power plant in March 2011 were exonerated of criminal responsibility by the Tokyo District Court on Sept. 19.
The three former executives of Tokyo Electric Power Co. pleaded not guilty to a charge of professional negligence resulting in death and injury related to the outbreak of the nuclear crisis triggered by a massive earthquake and tsunami.
In reaching the decision, the court stated that tsunami forecast information the three were made aware of, a key focus of the case, "had no specific basis," and that they could not have realistically foreseen a disaster of such magnitude.
The case was brought to the court after an inquest of prosecution committee comprising lay citizens decided the three should be put on trial.
Tsunehisa Katsumata, 79, a former chairman; Ichiro Takekuro, 73, a former vice president; and Sakae Muto, 69, also a former vice president, faced trial on grounds they failed to take action to prevent the accident despite forecasts that a tsunami exceeding the roughly 10-meter height of the main plant facilities could overwhelm the site.
In the event, towering tsunami knocked out reactor cooling systems, triggering a triple meltdown and release of hazardous materials into the atmosphere.
The nuclear accident prompted mass evacuations in neighboring areas.
This included moving patients from Futaba Hospital about 4.5 kilometers away, ultimately resulting in the deaths of 44 of them from malnutrition and dehydration during the evacuation process itself or after they arrived at evacuation sites.
In its ruling, the Tokyo District Court said the three executives first became aware of the possibility of tsunami exceeding 10 meters hitting the plant site between June 2008 and February 2009. It added that it was not clear if anti-flood measures at the site or relocating facilities to higher ground would have been completed before the magnitude-9.0 earthquake, even if the work started started soon after they learned of the tsunami threat.
The court said the only way the nuclear accident could have been prevented was if plant operations had been stopped by early March, but added that making such a decision required careful consideration based on safety standards in place at the time, given the usefulness of nuclear plants in supporting the economy and people's lives.
The court then turned to whether the three executives could have foreseen that a huge tsunami exceeding 10 meters might hit the site, saying that the estimate made by a TEPCO subsidiary in March 2008 that a maximum 15.7-meter tsunami might hit was "decisively important information."
However, the court said the central government's long-term earthquake forecast used as a basis for the estimate "had no specific basis, had been questioned by experts and was not reflected in disaster management plans compiled by local governments."
Based on these factors, the court said the information was not something that would have alerted the executives to the possibility of an overpowering tsunami and made it very difficult for them to decide to halt operations at the plant given the various negative effects such action would have produced.
During the trial, the former executives apologized to victims of the nuclear crisis and bereaved family members, but maintained their innocence on the question of negligence.
The lawyers serving as prosecutors had sought five-year prison terms for each of the trio.
They argued that all executives at the highest level were obligated to "constantly gather specific information related to safety, as it was their duty to implement thoroughgoing measures," in light of the potential for a catastrophic accident.
The prosecutors argued that the three former executives chose to overlook much of the information they were party to on numerous occasions, citing as a typical case the estimate by the TEPCO subsidiary.
In June of 2008, when Muto received a report on the estimate, he instructed that the forecast be assessed by the Japan Society of Civil Engineers, which prosecutors argued was inappropriate, as it led to delays in implementing key safety measures.
At a meeting in February 2009 of the highest levels at TEPCO, the three defendants, all in attendance, listened to a report from a department head in charge of the matter who said it was possible that a tsunami 14 meters high could strike the Fukushima plant.
The prosecutors said that despite such information, the three failed to order a higher embankment to be built around the plant site or halt operations, as they were more concerned about the adverse effects such actions would have on TEPCO's balance sheet.
However, the three former executives and their lawyers defended the decisions.
Muto said it was only natural to turn to specialists to confirm the long-term earthquake forecast, as he was doubtful about its reliability. He denied that the instruction was meant to delay action being taken.
Regarding the calculation of 15.7 meters, Takekuro said he was told by a department head that it was not 100 percent reliable.
Katsumata also said he felt that the statements made in the 2009 meeting by the department head were made in a tone that made the presented information sound unreliable.
Defense lawyers also argued that the 15.7-meter calculation was in line with a forecast that said a tsunami would likely come from the south, while the actual tsunami struck the east side. They argued that since building an embankment on the south side would not have prevented the nuclear accident, they could not be blamed for failing to carry out their obligations.
The ruling on the case is the culmination of actions that go back to June 2012 when residents of Fukushima Prefecture submitted criminal complaints against TEPCO executives and central government officials in an effort to determine their criminal responsibility for the nuclear accident.
However, the Tokyo District Public Prosecutors Office decided not to indict anyone named in those complaints, leading to a prosecution inquest panel finding on two separate occasions that the three former executives should be indicted and made to stand trial.
The prosecution inquest panel system was introduced in May 2009 as part of judicial reforms that also saw the start of the lay judge system. If eight of 11 citizens chosen for the panel agree that an indictment is warranted on two separate occasions, the individual named must stand trial and face lawyers designated by the court to serve as prosecutors.