Japan’s highest court says judges cannot overturn a lower court’s ruling in a second trial without presenting detailed, concrete proof that the initial ruling was irrational.

The Supreme Court of Japan dismissed the ruling of Tokyo's High Court against a former business executive who had been indicted for smuggling stimulants to Japan.

The business executive, Kikuo Anzai, was exonerated by lay judges in the first trial. But prosecutors appealed the ruling and the Tokyo High Court reversed the original acquittal.

Presiding Justice Seishi Kanetsuki of the Supreme Court said when overturning a lower court’s ruling, the second court must provide concrete proof that the initial ruling was irrational in terms of "logical consistency and common sense."

Anzai was the first person to receive a complete acquittal by lay judges since a lay judge trial system was introduced in 2009. The Tokyo High Court's overturning the lower court's acquittal also generated a dispute over the effectiveness of the lay judge trial system.