On This Day in 1993 – David Mason, the last to enter California’s gas chamber.

The gas chamber has long been America’s most controversial, debatable, complicated and expensive way to execute its condemned. Since the world’s first judicial gassing (Gee Jon in Nevada in 1924) it has been used by eleven states to execute hundreds of convicts. Serial killer David Mason was the 196th convict to enter California’s chamber and the last in the Golden State to do so.

Shortly after Mason’s death Federal Judge Marylin Hall Patel ruled on a lawsuit brought by California’s condemned citing the gas chamber as cruel and unusual punishment. After reviewing the evidence and watching video footage of the gassing of Robert Alton Harris on 21 April 1992 Judge Patel (long opposed to the gas chamber) issued an historic ruling.

Until then no specific execution method had been ruled unconstitutional despite numerous legal battles to do so. Patel’s ruling applied only within California, then one of five states still using lethal gas. It was the end of what California’s condemned called the ‘time machine, ‘coughing box, ‘smokehouse’ or ‘the little green room.’ From then on California’s condemned would die by lethal injection.

Mason and Harris had been the only gassings in California since armed robber and cop-killer Aaron Mitchell. Mitchell, gassed in 1967, had attempted suicide hours before his execution and had had to be dragged kicking and screaming for the dozen steps between his holding cells (known as the Ready Room) and the chamber. Even after he was strapped in one of the chamber’s two perforated steel chairs Mitchell was still screaming ‘I am Jesus Christ!’

The gas silenced him permanently minutes later. For years the chamber too was silenced, lying almost abandoned until Harris died on 21 April 1992. Mason’s death came while the lawsuit resulting from Harris’s execution was still awaiting a ruling. The video footage of his death did as much as anything to convince Judge Patel that the chamber had no place in American penal policy. Discarded in California, it was seldom used elsewhere after her ruling.

Mason had murdered five people before being condemned to die. A long-time criminal with a lengthy record of arrests and incarceration, he had shown little remorse if any for the murders he had committed. Four elderly victims during robberies and a cellmate in the Alameda County Jail had died at his hands. All told he was widely viewed as a poster child for the death penalty rather than its abolition.

Mason, knowing he would only die in prison if he escaped the gas chamber, had decided to drop his appeals. Known as ‘Volunteers’ in America’s penal system, convicts choosing to die are not as rare as they might seem. Armed robber and killer Eddie Lee Mays (the last to be executed in New York) had given up in 1963, openly remarking he preferred the electric chair to spending the rest of his life behind bars.

Although afraid of the gas chamber Mason was prepared to face it rather than the rest of his life behind bars. If he was only going to die in prison anyway then, like Mays and numerous others before and since, he preferred to get it over with as soon as possible. The State of California was happy to oblige. It regarded Mason as a psychopath perfectly capable of telling right from wrong but fully prepared to rob and kill on a whim. Had Mason continued fighting his case it is likely he would have escaped the chamber only to receive lethal injection.

The preparations for his death had changed little since the chamber was first used in December 1938. In 1937 the Folsom Five’ had attempted to escape Folsom Prison murdering Warden Clarence Larkin in the process. In December 1938 Robert Cannon and Albert Kessel inaugurated San Quentin’s new method on 2 December, Wesley Eudy and Fred Barnes followed them on 9 December and Ed Davis died alone on 16 December. The first week for the chamber would remain one of its busiest. Cannon and Kessel had been numbers one and two. David Mason would be number 196.

The day before his death Mason followed the time-honored routine. He was escorted to one of the two Ready Room cells only feet from the chamber. He was medically examined and issued with the standard condemned clothing of blue jeans and a white T-shirt. Defying Mason’s own wishes, lawyers were still trying to get a last-minute stay of execution. Their efforts proved fruitless. Mason, convict C80300 in San Quentin’s register, hadn’t wanted another stay anyway. Refusing a last meal or to give any final statement, Mason wanted only iced water until the time came.

Had Mason wanted to appeal both his lawyer Mike Brady and Federal District Judge Ronald M. Whyte were ready to file and consider it. Prison staff had also made it absolutely clear to Mason that he only had to file one and it would likely be granted. Mason declined, holding to his stated intent of dying on schedule.

While Mason passed the time under constant supervision (‘death watch’ in prison parlance) other guards prepared a solution of 41% sulfuric acid mixed with distilled water. Lumps of sodium cyanide were placed in a cheesecloth bag and hung carefully above the pot that would receive the diluted acid. The straps were checked and the windows tested before being sealed around their edges with Vaseline to prevent leaks in the decades-old ‘smokehouse.’

All was ready, only time stood between Mason and just after midnight on 24 August 1993. In times past convicts were gassed or hanged at 10am on the first Friday of the month, a grim tradition that spawned the phrase ‘Black Friday.’ ‘Black Friday’ had long been discarded, convicts dying as and when the courts permitted. The ‘Big Sleep’ itself was also about to be discarded. The red-painted lever outside the apple green-painted gas chamber was about to be pulled for the last time.

Just after midnight the ritual began. Mason’s life and that of the chamber also ended. By 12:05am he was securely strapped into one of the chairs and the lever was pulled at around 12:09. It took Mason over three minutes to finally fall unconscious, contrary to Warden Daniel Vasquez telling him it would take only a few seconds.

Fourteen minutes later Mason was dead, a doctor standing outside the chamber listened through a specially-extended stethoscope and when Mason’s heart stopped beating the announcement came. Aside from Harris it was the first such announcement in California since Aaron Mitchell way back in 1967.

California’s gas chamber had claimed its last victim, at least by its original method. It would be converted into a lethal injection chamber thereafter, though could have been re-converted to a gas chamber quickly and easily if another convict chose that method. When Judge Patel issued her ruling the next year those allowed a choice lost their right to choose.

Judge Patel’s ruling came from a lawsuit Mason had declined to participate in. 12 April 1992 had seen Harris, David Fierro and Alejandro Ruiz file a complaint in Federal District Court to have lethal gas declared unconstitutional, a lawsuit backed by the American Civil Liberties Union of Northern California and Warren George and Carolyn Reid of Los Angeles law firm McCutcheon, Doyle, Brown and Enerson.

Judge Patel had issued a restraining order barring Harris from execution, an order overruled by the US Supreme Court which had also ordered Harris receive no further stays except from the Supreme Court itself, a highly unusual legal move. The result had been double-murderer Harris being taken in and out of the chamber before finally dying at around 6am instead of just after midnight. It had been Harris’s execution that Judge Patel had ordered be videotaped, a tape that she viewed and was later destroyed.

The case was both controversial and sometimes acrimonious. The plaintiffs made a powerful case based on eyewitness testimony and San Quentin’s own execution records. Scientific evidence on the speed and effectiveness of cyanide gas further bolstered their case. The State of California offered testimony only from a US Army pharmacologist and toxicologist.

By far the most damning evidence regarded the State of California’s ties to Fred Leuchter. A self-proclaimed execution expert, Holocaust-denier and fraudulent ‘engineer’ (later found to be practising without an engineering license), Leuchter had invented a lethal injection machine and advised on electrocutions and the gas chamber for a number of US states including California. The so-called ‘Mr. Death’ had been responsible for refurbinshing San Quentin’s gas chamber.

Merely being associated with such a character as Leuchter further discredited California’s case (which had been none too strong to start with). The case began on 25 October 1993, ending on 5 November. On 4 October 1994 Judge Patel’s ruling finally shot the ‘smokehouse down.’ Patel declared California’s gas chamber cruel and unusual punishment violating the Eighth Amendment to the Constitution. It was the first time a Federal court had ruled a specific method to be unconstitutional.

The ruling had an effect far outside California itself. It was upheld in 1996 by the Ninth Circuit Court of Appeals in another unprecedented Federal court ruling. California was now unable to use its gas chamber as a gas chamber by Federal court order. It would never do so again. The chamber was converted into a lethal injection facility instead.

The stories of the Folsom Five and Aaron Mitchell can be found in my forthcoming book ‘Murders, Mysteries and Misdemeanors in Northern California,’ published on August 28 2020. My previous book ‘Murders, Mysteries and Misdemeanors in New York‘ is currently available.

2 responses to “On This Day in 1993 – David Mason, the last to enter California’s gas chamber.”

  1. […] Federal level. Alabama, meanwhile, looks set to trial lethal gas, not the previous use of cyanide declared cruel and unusual in California, nut the new method of nitrogen asphyxia in which Oklahoma has indicated an interest. Alabama, too […]


  2. […] convicts whose fates remain undecided. California last used its chamber to execute David Mason in 1993. In 1994 Federal District judge Marilyn Hall Patel ruled its further use to be cruel and […]


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