Photo/Illutration The sign outside the Tokyo District Court building (Asahi Shimbun file photo)

Family members of Aum Shinrikyo doomsday cult leader Chizuo Matsumoto filed a lawsuit against the state seeking 1 million yen ($8,656) in damages on grounds his July 2018 execution was illegal because he was mentally incompetent.

Matsumoto, who was aged 63 when he was hanged at the Tokyo Detention House, was accused of masterminding the March 20, 1995, sarin gas attacks on the capitals subway system that resulted in 14 deaths and sickened thousands, as well as other acts of murder by his disciples.

The plaintiffs lawyers cited a provision in the Criminal Procedure Law that an execution must be stayed if a death row inmate is deemed to be mentally incompetent.

The lawyers contended that Yoko Kamikawa, the justice minister who signed his death warrant, “issued the execution order unthinkingly, which constituted negligence of duty.” They said she should have checked Matsumotos medical records and ordered a psychiatric evaluation.

Matsumoto reigned over the cult using the name Shoko Asahara.