The gas chamber was first adopted in the U.S. state of Nevada in 1921 in an effort to provide a more humane form of capital punishment. On February 8, 1924, Gee Jon became the first person to be executed by lethal gas. By 1955, 11 U.S. states had adopted the gas chamber as their method of execution, but by the early 21st century it was available in only two states (California and Missouri), where condemned prisoners were allowed to choose between lethal injection and lethal gas. In Arizona, inmates sentenced to death before November 1992 were allowed to choose between lethal injection and lethal gas; in Wyoming, lethal gas was designated to replace lethal injection if the latter method was ruled unconstitutional. From 1921 to 1972 (when the U.S. Supreme Court commenced its moratorium on the death penalty), lethal gas was applied in some 600 executions; from 1976 (when the moratorium ended) to 1999 it was used in only 11 executions. The high cost of renovating disused gas chambers, as well as a growing perception of the method as unconstitutionally cruel, contributed to this trend, leading some scholars to predict in the early 21st century that the method would not be used again.
California’s lethal gas procedure (the most thoroughly documented) was carried out in a sealed, modified octagonal chamber. The inmate was strapped to a chair with holes in the seat, below which was placed a container of sulfuric acid, distilled water, and sodium cyanide crystals. The executioner pulled a lever that mixed the cyanide crystals into the sulfuric acid–water container to create the hydrocyanic gas that the inmate inhaled. Although there is a consensus that cyanide affects many parts of the body, it is unclear at which point an individual becomes unconscious or dies, because pain and consciousness are difficult to measure. In 1996 a federal appeals court unanimously held that California’s statute authorizing lethal gas violated the U.S. Constitution’s Eighth Amendment prohibition against cruel and unusual punishments, based on a lower court’s conclusion that gassed inmates can suffer an extreme amount of pain and that there is a substantial likelihood that such pain would last for several minutes. (Over time, eyewitnesses had also reported a number of long and gruesome lethal gas executions in California and other states.)
The U.S. Supreme Court has never ruled on the constitutionality of lethal gas. It did, however, vacate the federal appeals court ruling that lethal gas was unconstitutional because the California legislature called for lethal injection unless a prisoner specifically requested lethal gas. The United Nations Human Rights Committee has considered California’s gas chamber torturous and inhumane.
Outside the United States no other country has adopted lethal gas as a constitutional method of carrying out capital punishment. During the Holocaust, however, Nazi Germany employed gas chambers for the purpose of killing Jews and other targeted groups. The chambers were established at concentration camps and usually disguised as bathhouses. Men, women, and children were herded naked into the chambers after being told that they were going to take showers. The doors were closed, and poison gas was injected.