Maryland, which has not executed a prisoner since 1961, is one of three states to rely exclusively on the gas chamber, a method criticized by some doctors and civil liberties advocates as inhumane.
Only Maryland, Arizona and California, where Robert Alton Harris was executed yesterday, continue to use the gas chamber. Two others give condemned prisoners a choice between the gas chamber and lethal injection.
By a 7-2 margin, the U.S. Supreme Court rejected a last-minute appeal by Harris' lawyers claiming that the gas chamber violated the Constitution's prohibition on cruel and unusual punishment.
In a blistering dissent, Justice John Paul Stevens wrote, "The barbaric use of cyanide gas in the Holocaust, the development of cyanide agents as chemical weapons, our contemporary understanding of execution by lethal gas, and the development of less cruel methods of execution all demonstrate that execution by cyanide gas is unnecessarily cruel."
Several states have abandoned the gas chamber in favor of lethal injections in the last decade.
Maryland used to hang its condemned prisoners but switched to gas as a more humane method in 1955. The question has been moot in Maryland, which has not executed anyone since Nathaniel Lipscomb, a convicted rapist and murderer, 31 years ago.
Eleven men are now under sentence of death in Maryland. It could take "a couple of years" for any of them to exhaust their appeals, said Gary E. Bair, chief of the criminal appeals division of the state attorney general's office.
"I've heard many horror stories" about gas chamber executions, said Katy O'Donnell, an attorney in the state public defender's death penalty unit. "Stories about taking 11 minutes to die, or 13 minutes to die. It seems like extreme cruelty."
In medical circles, there seems little disagreement that lethal injection is the least painful method of execution. This is because the condemned prisoner first receives an intravenous drug that puts him to sleep, making him unaware of the cardiac and respiratory arrest brought on by two other drugs.
How much prisoners suffer in the gas chamber has been widely debated. Dr. Bill Eckert, a forensic pathologist in Wichita, Kan., said prisoners become unconscious within a half-minute and do not struggle through the suffocation that occurs over the next six to 10 minutes.
But Dr. Robert H. Kirschner, deputy medical examiner in Chicago, said witnesses have described prisoners thrashing about for "eight to 10 minutes" with movements that are clearly voluntary, suggesting that some people endure many minutes of conscious suffering.
Maryland officials could not say why the state had not abandoned the gas chamber.