The trial of three former top executives of Tokyo Electric Power Company Holdings Inc. over the March 2011 meltdowns at its Fukushima No. 1 nuclear power plant focused on whether the executives were able to foresee in concrete terms the possibility of a giant tsunami flooding the facility — as it did in the Great East Japan Earthquake — and whether they neglected to take steps to avert the catastrophe. In acquitting the three executives of the charges against them, the Tokyo District Court determined that they could not predict the onslaught of a giant tsunami to the extent that obliged them to halt the plant's operation to avoid a major accident.

Along with the criminal trial of the former executives, Tepco and the central government have become the target of civil lawsuits over their responsibility for the Fukushima nuclear disaster. More than 10,000 people displaced in the aftermath of the crisis have filed some 30 suits across the country, seeking damages from the government and the power company. Court decisions in several cases recognized that Tepco knew about the risk of a giant tsunami hitting the plant but neglected to take measures against such an eventuality and ordered the firm to pay damages.

The three former Tepco executives stood trial on a mandatory indictment by a prosecution inquest panel of citizens after prosecutors twice decided not to file charges against them. They were accused of professional negligence over the death of 44 patients at a local hospital who died as they were forced to evacuate in the wake of the nuclear accident. In a criminal trial, which identifies the responsibility of accused individuals and punishes them if they're found guilty, the demands for proof and evidence are more stringent than in civil lawsuits, and the hurdles for establishing criminal responsibility are far higher. In a sense, the acquittals of the former Tepco executives highlight the limitations of criminal trials in pursuing the responsibility of executives of large firms for serious accidents.