In the first hearing of the trial at Tokyo district court on 30 June, the executives pleaded not guilty to the charges in the only criminal action that has been brought against officials.
Tsunehisa Katsumata, chairman of Tokyo Electric Power (Tepco) at the time of the environmental disaster, and two other former executives, told the court that they could not have foreseen a tsunami of the size that knocked out the facility's backup cooling system, causing a meltdown in three reactors on 11 March 2011.
The reactor failures led to radioactive releases and triggered a 30km evacuation zone around the plant.
Prosecutors allege that Katsumata and his co-defendants -- former Tepco vice-presidents Sakae Muto and Ichiro Takekuro -- had been presented with data that anticipated a tsunami more than 10m in height. A wave of this height could cause a power outage and other serious damage because the plant's seawall was not robust enough to withstand it.
The Guardian highlighted a government panel report, which said that Tepco had simulated the impact of a tsunami on the plant in 2008. The operator had concluded that a wave measuring up to 15.7m could hit the nuclear facility if a magnitude-8.3 quake occurred off the coast of Fukushima. Executives allegedly ignored the internal study findings.
Investigators have been highly critical of Tepco's safety culture and also pointed to poor oversight by industry regulators. The Guardian reported that prosecutors had considered the case twice and dropped it both times. However, a citizens' judicial panel overrode the decision and indicted the former executives.
Prosecutors allege that the executives should be held to account for the deaths of 40 elderly people, who had to be evacuated from a hospital near the plant. There are no records of anyone dying as a result of radiation exposure from the facility.
If convicted, the three former executives face up to five years in prison or a penalty of up to 1m yen (£7,000).