The head of a group studying cults said Monday that former AUM Shinrikyo members on death row should not be executed as their experience could help to prevent crimes by such individuals.

It is important to conduct studies with them to map out how they came to recognize their wrongdoing, Kimiaki Nishida, chairman of the Japan Society for Cult Prevention and Recovery said at a press conference the day before the 23rd anniversary of the sarin nerve gas attack by the doomsday cult on the Tokyo subway system.

"The question is what triggered that change (in their minds). How did their minds change? How did the transition occur? How did they return to themselves?" Nishida, a social psychologist, said at the Foreign Correspondents' Club of Japan.

The 1995 gas attack masterminded by AUM founder Shoko Asahara, 63, killed 13 people and left more than 6,000 people ill.

Last week, seven of the 13 former AUM Shinrikyo members on death row were transferred from the Tokyo detention center to other facilities, stirring speculation that the state might be preparing to execute them for a series of crimes that left 29 people dead.

The study group believes the inmates' sentences should be commuted to life imprisonment and has submitted a written plea to spare their lives to Justice Minister Yoko Kamikawa, Nishida said.

But the JSCPR has not taken a position on whether Asahara, whose real name is Chizuo Matsumoto, should be executed as its members are divided, Taro Takimoto, a board member of the group, said at the press conference.

"Asahara was the brain, and the other 12 merely worked for him," said Takimoto, a lawyer who represented victims of AUM Shinrikyo, referring to another sarin attack that targeted him more than two decades ago.

"I believe these 12 should repent for the rest of their lives...and convey their thinking to the public so that this AUM Shinrikyo group can be destroyed and such atrocities are not repeated," he said, referring to Aleph and other splinter groups of the cult.

Given the 12 death row inmates were involved in vicious criminal activities and know how they ended up committing these crimes, they should be able to aid with the understanding of such cult groups, the JSCPR said in a statement last week.

Still some relatives of the victims have said all 13 of the death row inmates should be executed.