The Supreme Court has upheld a lower court's acquittal of three former presidents of West Japan Railway Co. over a 2005 derailment that killed 106 passengers and the driver in Amagasaki, Hyogo Prefecture.

Rejecting an appeal filed by lawyers who served as prosecutors in the case, the top court's Second Petty Bench, led by Justice Tsuneyuki Yamamoto, said in its decision dated Monday that the former JR West presidents "could not have foreseen that the curve at the site of the accident posed a high degree of danger."

JR West President Tatsuo Kijima told reporters on Tuesday, "The criminal trial is over, but it does not lessen the seriousness of the accident."

"With a resolve never to let such an accident occur again, we want to fulfill our responsibility to keep enhancing safety," he said at the company's headquarters in Osaka in western Japan.

 Japan marks 12th year since deadly train derailment

A rapid service train on the JR Fukuchiyama Line derailed and crashed into a condominium building in Amagasaki during the morning rush hour on April 25, 2005, after failing to negotiate the tight bend in the track. The accident left 562 people injured.

Relatives of the victims voiced dissatisfaction and anger.

"I can't understand why the appeal (made in April 2015) was rejected all of a sudden after so long," said Hiroshi Ueda, 62, who lost his 18-year-old son Masaki in the accident.

"Despite causing such a grave accident, the probe into the cause of the accident was insufficient and nobody is taking responsibility. How can we expect public transportation to ever become truly safe," he said.

Mitsuko Fujisaki, 77, who lost her 40-year-old daughter, also expressed disappointment.

"It has only been 12 years since the accident. I don't think this puts an end" to efforts to find who was responsible for allowing lax train operations, she said.

The three defendants -- Masataka Ide, 82, Shojiro Nanya, 75 and Takeshi Kakiuchi, 73 -- had served as presidents during the period between when the railway operator made the curve tighter in 1996 and when the accident occurred.

Initially, prosecutors only indicted Masao Yamazaki, 74, also a former president, and dropped charges against the three on the grounds that there was insufficient evidence against them.

Yamazaki was cleared of professional negligence resulting in death and injury by a district court in 2012.

A Committee for the Inquest of Prosecution, a panel of citizens tasked with reviewing criminal cases, later decided twice that the three should be indicted for professional negligence resulting in death and injury, prompting their mandatory indictment by court-appointed lawyers serving as prosecutors.

The focal point of the trial was whether the defendants were able to foresee the possibility of a derailment and should have installed a computerized safety mechanism known as the automatic train stop system, or ATS.

Court-appointed lawyers argued that the three led the tightening of the curve and revisions to timetables for train services on the line in a manner that would make it harder for drivers to run trains on time. The lawyers argued that the three neglected to install an ATS, although they could have foreseen the possibility of an accident.

But the top court said the defendants "could not have foreseen that the accident site posed a particularly high risk among more than 2,000 similar curves in the company's operating area," while noting that there were no rules at the time that required railway operators to install an ATS and the three were not in a position to grasp detailed information taken from the field.

Both the Kobe District Court and the Osaka High Court had found the three not guilty as they could not have foreseen the possibility of a derailment. Lawyers acting as prosecutors had filed an appeal to the Supreme Court.

 Japan to mark 12th anniversary of deadly train derailment