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Sufferers of Minamata Disease Won an Important Case in
Japanese Supreme Court against the National and Prefectural Governments

Dr. Shigeo Ekino (MD)
Professor, Graduate School of Medical Sciences, Kumamoto University
Honjo 1-1-1, Kumamoto City 860-8556 Japan

Dr. Tadashi Ninomiya (MD)
Assistant Professor, Graduate School of Medical Sciences, Kumamoto University

Mari Susa
Associate Professor of Law, Kumamoto University

April 25, 2006

The Japanese Supreme Court ruled on October 15, 2004, nearly 50 years since the official recognition in 1956 of the poisoning known as Minamata disease, that the national government and the prefectural government of Kumamoto were held to be legally responsible for the outbreak. Minamata disease is a form of methlymercury (MeHg) poisoning caused by ingesting methylmercury in contaminated fish and shellfish. The effluent containing methylmercury compounds which were produced as a by-product in the acetaldehyde plant of the Chisso corporation was discharged into Minamata Bay and subsequently into the Minamata River causing this widespread poisoning.

In 1982, the plaintiffs, former residents of areas in and around Minamata who had moved to the Kansai area in the 1960's, brought a case before the Osaka District Court claiming damages from both governments as well as the polluter, the Chisso corporation. This case was the first of its kind and named the "Kansai Lawsuit" after the claimants' place of current residence. Other lawsuits of the same kind were subsequently filed in Tokyo, Kyoto, and Fukuoka.

The central issue of the case was whether it could be proven that the plaintiffs who moved away from Minamata were victims suffering from the poisoning which took place decades ago. If they could be identified as the sufferers of Minamata disease, they would satisfy one of the necessary conditions for entitling them to receive compensation. The definition of Minamata disease has been an issue of controversy for decades due to its interconnection with the certification system, the intransient government authorities' procedure for officially recognizing sufferers of Minamata disease. Victims could not simply be diagnosed as having Minamata disease; they have had to be officially certified before they could be recognized as suffering from Minamata disease.

The definition of Minamata disease was moreover confused by outdated science resulting from the absence of any extensive survey to study how much, how far, and how long the poisoning had occurred.

After losing the case in the Osaka District Court, the lawyers for the Kansai Lawsuit plaintiffs changed the course of their argumentation, dropping the archaic definition of Minamata disease and instead claimed plaintiffs' rights based on new scientific findings researched by Dr. Shigeo Ekino and colleagues. This research was part of the long-term investigation undertaken into the effects of MeHg poisoning with control studies examining the people living in the polluted area and those living in a non-polluted area: case-control epidemiological research.

Ekino gave evidence in the Osaka High Court litigation based on these research findings. The judges assimilated science in their deliberative process and found the evidence submitted in the testimony compelling. This led to the Osaka High Court ruling in 2001 that held both national and Kumamoto prefectural governments in part responsible from January 1960 onward for the cause and spread of Minamata disease, damage which could have been prevented if the government authorities had taken appropriate measures. The Supreme Court upheld the Osaka High Court ruling.

The Supreme Court ruling was a landmark ruling in that it established the legal responsibility of government authorities by bringing scientific testimony into the court of law. This ruling in the highest court of the judiciary is an exhortation to the other branches of government, the administrative and legislative, for having failed to properly give relief to the suffers of Minamata disease and thus alleviate this protracted case.

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