In a baffling ruling, the Tokyo District Court on Sept. 19 acquitted three former top Tokyo Electric Power Co. executives of criminal liability for the catastrophic accident that ruined the utility’s Fukushima No. 1 nuclear power plant with devastating consequences for society.

In determining the case, the court assumed that the only way the nuclear accident in 2011 could have been prevented was if plant operations had been halted before the quake. Under this assumption, it considered whether the three former executives could have foreseen that a huge tsunami might hit the plant with a certainty that demanded that they take drastic action.

The court then examined the central government's long-term earthquake forecast published in 2002, which said a gigantic earthquake could take place anywhere in wide sea areas stretching from off the Sanriku part of the Tohoku region, which was devastated by the 2011 Great East Japan Earthquake, to off the Boso Peninsula in Chiba Prefecture.

The ruling dismissed the importance of this projection, saying it had no solid basis and questionable credibility.

Pointing out that nuclear plants are important infrastructure that supports people’s life in society and economic activity, the ruling argued the former TEPCO executives were under no obligation to shut down the reactors.

In lawsuits filed by victims of the accident seeking compensation from the central government and the utility, the courts have mostly upheld the plaintiffs’ claim that the tsunami was predictable because of the government’s long-term quake forecast.

Multiple rulings in these suits said the accident could have been prevented if some simple measures had been taken, such as relocating the plant’s emergency power source to high ground.

In criminal cases, claims must be proved more rigorously than in civil cases. Even so, the latest ruling takes a surprisingly different stance toward the predictability of the tsunami from other court decisions concerning the matter.

The exoneration of the three men, the only individuals indicted over the accident, means no one in a senior management position as the operator of the plant will be held responsible for the unprecedented nuclear disaster in this nation. The court decision has left it doubtful whether the trial has provided sufficiently convincing answers to key questions.

Still, the trial has offered some important insights into the accident through arguments at the open court.

Many important facts that were not mentioned in the probes by the government or the Diet have come to light.

For instance, the government’s long-term prognostication concerning mega-quakes prompted TEPCO to start serious debate on additional safety measures, including the construction of a seawall. Measures to protect the plant from tsunami were also discussed in meetings attended by top executives.

But Tsunehisa Katsumata, 79, a former chairman, said he had had “no interest” in the issue. The other two defendants repeatedly said they had “no memory” of such discussions. The three tried to pass off responsibility onto each other as they proclaimed their innocence.

It is distressing to learn that such an organization and people have been operating a nuclear power plant for so long with the government, which is supposed to exercise effective oversight over the operator, raising no questions about their qualifications. The accident was a consequence of this dire situation.

This problem should not be dismissed as belonging to the past or being unique to TEPCO.

In recent years, a raft of new challenges concerning the safety of nuclear power generation have emerged, including the risks of major volcanic eruptions or terrorist attacks.

But electric utilities operating nuclear plants are lobbying the Nuclear Regulation Authority to allow them to put off taking measures necessary for dealing with these risks, claiming such efforts would require enormous amounts of time and money.

We cannot help but wonder what they have learned from the Fukushima disaster.

The trial of the three former TEPCO executives has raised many important questions and challenges. What should be done to make nuclear plant operators sufficiently sensitive to the small but real risks of a major crisis occurring, for instance? What kind of nuclear safety regulations should we have? Does nuclear power have a future in this disaster-prone nation?

Society as a whole should confront all these questions and challenges.

--The Asahi Shimbun, Sept. 20