In 1924, the use of cyanide gas was introduced as Nevada sought a more humane way of executing its inmates. Gee Jon was the first person executed by lethal gas. The state tried to pump cyanide gas into Jon's cell while he slept. This proved impossible because the gas leaked from his cell, so the gas chamber was constructed. (Bohm, 1999) Today, five states authorize lethal gas as a method of execution, but all have lethal injection as their primary method. A federal court in California found this method to be cruel and unusual punishment. The last use of a gas chamber was on March 3, 1999, when Walter LaGrand, a German national, was executed in Arizona.
For execution by this method, the condemned person is strapped to a chair in an airtight chamber. Below the chair rests a pail of sulfuric acid. A long stethoscope is typically affixed to the inmate so that a doctor outside the chamber can pronounce death. Once everyone has left the chamber, the room is sealed. The warden then gives a signal to the executioner who flicks a lever that releases crystals of sodium cyanide into the pail. This causes a chemical reaction that releases hydrogen cyanide gas. (Weisberg, 1991)
The prisoner is instructed to breathe deeply to speed up the process. Most prisoners, however, try to hold their breath, and some struggle. The inmate does not lose consciousness immediately. According to former San Quenton, California, Penitentiary warden, Clifton Duffy, "At first there is evidence of extreme horror, pain, and strangling. The eyes pop. The skin turns purple and the victim begins to drool" (Weisberg, 1991).
Caryl Chessman, before he died in California's gas chamber in 1960, told reporters that he would nod his head if it hurt. Witnesses said he nodded his head for several minutes (Ecenbarger, 1994). According to Dr. Richard Traystman of John Hopkins University School of Medicine, "The person is unquestionably experiencing pain and extreme anxiety...The sensation is similar to the pain felt by a person during a heart attack, where essentially the heart is being deprived of oxygen." The inmate dies from hypoxia, the cutting-off of oxygen to the brain (Weisberg, 1991).
At postmortem, an exhaust fan sucks the poison air out of the chamber, and the corpse is sprayed with ammonia to neutralize any remaining traces of cyanide. About a half an hour later, orderlies enter the chamber, wearing gas masks and rubber gloves. Their training manual advises them to ruffle the victim's hair to release any trapped cyanide gas before removing the deceased (Weisberg, 1991).
In 2015, Oklahoma adopted the use of nitrogen gas in executions if lethal injection cannot be performed. Though not poisonous, in a closed environment the nitrogen would deprive the inmate of oxygen, causing death. It has never been used in an execution.