The judge says Masami Tsuchiya's crimes were premeditated.
Finding clear murderous intent, the Tokyo District Court handed the death sentence to former senior Aum Shinrikyo "No. 2 health minister'' Masami Tsuchiya on Friday.
Tsuchiya, 39, was indicted for murder in connection with two fatal sarin nerve-gas attacks and for manufacturing deadly chemicals.
The most serious charges concerned the 1995 sarin attack on the Tokyo subway system that left 12 people dead and thousands injured, and a similar assault the year before in Matsumoto, Nagano Prefecture, that killed seven and hurt hundreds.
Judge Satoru Hattori said the crimes were premeditated and carried out in collusion.
Tsuchiya is the 11th cultist to be sentenced to death by district courts or at their first trials.
Aum Shinrikyo, under its leader, Chizuo Matsumoto, attempted to foment revolution.
Sentencing for Matsumoto, 48, who ruled the cult under the name Shoko Asahara, is set for Feb. 27. Prosecutors are seeking the death penalty.
Tsuchiya faced seven indictments: for murder, attempted murder and other crimes, including incidents involving the use of toxic VX gas.
Prosecutors sought the death penalty at the outset, saying Tsuchiya was a key figure in the manufacture of chemical weapons. They noted he held a master's degree from Tsukuba University in organic chemistry.
As in most cases concerning the death penalty, Hattori read his opinion before sentencing.
Addressing the sarin attack in Nagano Prefecture in 1994, the judge took note that Tsuchiya had told investigators, "I knew cult officials were planning to kill an unspecified number of people.''
The judge concluded there were no mitigating circumstances.
"Without the defendant, the cult would not have been able to pull off a crime that used chemical weapons,'' the judge said. "The defendant's role was the crux of the crime. His responsibility is indeed grave.''
Hattori noted Tsuchiya was unrepentant and had never apologized to the bereaved or the victims. "He must pay with his life.''
As for the sarin attacks in the capital, Hattori ruled there was sufficient reason to believe "the defendant knew the sarin he had manufactured was going to be used in a subway attack.'' That, he said, made him "a partner in crime'' rather than a supporting player.
Tsuchiya had admitted his involvement in manufacturing deadly chemical agents, but had maintained throughout his trial that: "There was actually no sarin contained in the liquid that was sprayed in Matsumoto.'' He had told the court: "I never thought sarin will be used in the subway (attack).''
He admitted only to illegal possession of drugs and had alluded often to his continuing allegiance to his "guru,'' Matsumoto.
On numerous occasions Tsuchiya uttered remarks apparently aimed at shielding his spiritual leader while taking the stand as a defense witness.
Tsuchiya arrived in court Friday in his usual attire-purple sweatshirt, pants and socks. Aum Shinrikyo cultists always wore purple.
Tsuchiya uttered an almost inaudible "yes'' when asked to confirm his name in court. He listened intently with his eyes closed while the judge read his opinion and sentence-a marked contrast from previous cockiness in court, marked by outbursts over statements made by prosecutors.