Photo/IllutrationThe former executives of Tokyo Electric Power Co. facing trial at Tokyo District Court are, from left, Tsunehisa Katsumata, a former chairman, Sakae Muto, a former vice president, and Ichiro Takekuro, another former vice president. (Asahi Shimbun file photo)

Final arguments were heard March 12 in a criminal case involving three former Tokyo Electric Power Co. executives and their role in the 2011 disaster at the Fukushima No. 1 nuclear power plant.

The defendants--Tsunehisa Katsumata, 78, a former chairman; Sakae Muto, 68, a former vice president; and Ichiro Takekuro, 72, another former vice president--maintained their innocence, saying they had no way of knowing a massive tsunami triggered by the March 11, 2011, Great East Japan Earthquake would lead to the triple meltdown at the Fukushima No. 1 nuclear power plant.

The three are charged with professional negligence resulting in death and injury.

The case was brought to the Tokyo District Court after an inquest of prosecution committee made up of lay citizens decided the three should be put on trial.

The lawyers serving as prosecutors are seeking five-year prison terms for each of the defendants.

A verdict will be read on Sept. 19.

The major point of contention during the trial was an assessment by a TEPCO subsidiary in 2008 that a tsunami of 15.7 meters was the maximum height that could strike the Fukushima complex.

Defense lawyers asserted that the central government's long-term earthquake forecast, upon which the subsidiary's calculation was based, was unreliable.

After being briefed on the calculation, Muto arranged for the forecast to be assessed by the Japan Society of Civil Engineers.

Defense lawyers stressed that decision was a rational one and in no way could be construed as a delay in taking steps to counter the threat of destructive tsunami.

They also argued that prior to the Great East Japan Earthquake no forecasts existed of a possible magnitude-9.0 earthquake striking offshore.

For those reasons, the lawyers said their clients were innocent. They contended that there was no possible way the outcome could have been avoided, given the lack of a forecast of a disaster on such a scale.

Prosecutors argued that if operations at the Fukushima plant had been stopped five days prior to the earthquake and tsunami disaster, the nuclear accident could have been prevented.

In response, defense lawyers said that stopping operations would "have had a major effect on the lives of the people and on the industrial sector," adding that electricity fees would have risen if thermal power plants were used instead. They also said that stopping operations would have gone against government calls to reduce carbon dioxide emissions.

Defense lawyers said any decision to stop nuclear plant operations would have required a rationale that surpassed such considerations.

To gain guilty verdicts against the three former TEPCO executives, the lawyers serving as prosecutors had to show the defendants could have foreseen the danger of massive tsunami striking, and were negligent about taking necessary measures to guard against such an eventual outcome.