Thirteen former Aum members have been sentenced to death but none have been hanged so far. Only one cult member, Kazuaki Okazaki, has so far lost his final appeal against execution.
The defense lawyers said Nakagawa was not aware that the cult planned to release sarin in rush-hour Tokyo trains when he produced and packed the Nazi-invented gas.
Twelve people were killed and thousands more injured in the attack, which Asahara allegedly ordered in hopes of pre-empting a police raid on the cult.
The defense also said Nakagawa was only present to treat other Aum members from chemicals during the cult’s first sarin attack in 1994.
Seven bystanders died when the cult spread the gas in the central city of Matsumoto in an experiment ahead of the subway atrocity.
Nakagawa along with Okazaki was also convicted of involvement in the murders of an anti-sect lawyer, the lawyer’s wife and their one-year-old child.
The Tokyo District Court had found Nakagawa guilty on all 11 counts, with the judge saying: “The fact that total 25 people died in the attacks he took part in easily overwhelms the leniency that he deserves.”