The Supreme Court upheld the death sentence Monday for senior Aum Shinrikyo member Seiichi Endo for his role in two sarin attacks in the 1990s, effectively ending more than 16 years of investigation and trials involving the doomsday cult.

Endo, 51, a veterinarian and virologist, was condemned by lower courts for being the key architect of the nerve gas the cult used to deadly effect in 1994 in Matsumoto, Nagano Prefecture, and in the 1995 gassing of the Tokyo subway system.

Endo will be the 13th member of Aum to have his death sentence finalized. Condemned founder Shoko Asahara, 56, whose real name is Chizuo Matsumoto, was convicted of masterminding the cult's heinous crimes, and thus of murdering 27 people in 13 criminal cases.