Japan and the United States are the only two members of the Group of Seven advanced economies that have the death penalty.

Japanese death row inmates are executed by hanging. Three prison officers simultaneously press buttons to open the trap door so it is not clear which one is responsible.

Between 2012-2016, 24 people were executed, according to the most recent Justice Ministry data.

Unlike in the United States where execution dates are set in advance and made public, inmates in Japan are notified on the morning of their execution, usually about an hour before. The U.N. Committee against Torture has criticized Japan for “the psychological strain” on inmates and their families.

Only prison officials and a priest are present.

RELATED STORIES Aum founder Shoko Asahara was mentally competent during detention, sources maintain

Hangings are announced after the inmate is taken to the gallows. Since 2007 the ministry has released the names and crimes of those executed.

The seven Aum Shinrikyo members executed Friday at several facilities around the country may have been the largest number executed at any one time, said Akiko Takada of the anti-death penalty group Forum 90. A Justice Ministry official could not immediately confirm the claim.

Those sentenced to death can appeal up to the Supreme Court. The multiple Aum-related trials lasted more than 20 years.

Convicted inmates can seek a retrial even after a Supreme Court ruling, but this does not guarantee a stay of execution. Several of those executed Friday may have had requests for retrials pending, Amnesty International said.

The law says an execution must take place within six months of the sentence being finalized by the courts, but in practice it usually takes several years. The justice minister decides the timing.

The government, urged by the United Nations Human Rights Council to abolish the death penalty, said in 2008 it could not because public opinion favored it for “extremely vicious crimes.”

A 2014 government survey found that 80.3 percent of people supported the death penalty. That compares with 54 percent in the United States.

Anti-death penalty activists say a lack of information and increased interest in victims’ rights are partly behind the support.

In 2010, then-Justice Minister Keiko Chiba, who opposed the death penalty, signed off on two executions and opened an execution chamber to media for the first time, hoping to stimulate debate.

In 2016, a lawyers’ group called for the abolition of the death penalty by 2020, citing the possibility of wrongful convictions and international trends against capital punishment.