After a grisly history of electrocutions, gassings, hangings and firing squads, it is the cold, quiet science of lethal injections that has become America's most common and favored method of executing its worst criminals.
The U.S. Supreme Court ruled six years ago that such injections did not violate the Constitution's provisions against cruel and unusual punishment, clearing the way for states to administer the lethal cocktails under their own, sometimes secretive, protocols.
But a gruesome lethal injection gone wrong in Oklahoma has dealt death penalty supporters a potentially stunning setback this week, coming at a time when popular support for capital punishment has fallen and reliable lethal-injection chemicals are becoming harder and harder to get.
Clayton Lockett's unwieldy execution has triggered an already controversial internal investigation and prompted calls for a lethal-injection moratorium across the U.S., with experts predicting the Supreme Court will face greater pressure to rule on whether states can refuse to tell inmates the makeup of the drugs that are being used to end their lives.
"The public has a right to know how we are carrying out this very grave responsibility of the state," said Oklahoma state Sen. Connie Johnson, one of several state lawmakers calling Wednesday for a yearlong moratorium on executions in the state. "This is the worst thing that the government does. This ought to be the most transparent."
On Tuesday night, as witnesses watched from a prison viewing gallery in McAlester, executioners injected an experimental cocktail of lethal drugs into Lockett's body. The 38-year-old murderer was supposed to fall asleep before the drugs stopped his heart.
Instead, according to officials, one of Lockett's veins exploded, sending the inmate into a writhing, gasping fit that ended more than half an hour later with a fatal heart attack.
News of Lockett's bizarre demise drew instant criticism from death penalty opponents and even a rebuke from the White House on Wednesday.
"We have a fundamental standard in this country that even when the death penalty is justified, it must be carried out humanely," White House spokesman Jay Carney told reporters. "I think everyone would recognize that this case fell short of that standard."
Much of the criticism was directed at Oklahoma state officials, who had waged a long and extraordinary struggle to execute Lockett without providing details on the origin or quality of their lethal-injection drugs to his attorneys.
"The debacle in Oklahoma reveals the consequences of allowing execution protocols to remain secret," said University of Houston law professor David Dow. "The responsibility for inflicting this torture is widely shared by prosecutors, prison officials, judges and politicians, including the governor and attorney general in Oklahoma."
If there is such a thing as sympathetic death row inmates, Lockett probably wasn't among them. One night in 1999, Lockett kidnapped, raped and shot a young woman named Stephanie Neiman. He later coolly told investigators how he had watched his accomplices bury her alive, covering her in dirt as she gasped for life.
To execute Lockett, conservative state officials, led by governor Mary Fallin, ultimately forced (and won) a constitutional showdown with one of the state's highest courts over whether the state could be trusted to carry out the execution without complying with the defense's demands for details on where they obtained the drugs to be used.
Faced with growing opposition to the death penalty, particularly abroad, state prison authorities have had a hard time obtaining drugs from reputable manufacturers that can be used to paralyze an inmate and stop his heart. Instead, they have devised new and untested combinations of drugs.
When defense lawyers have objected and sought more information on the drugs, states such as Oklahoma have adopted laws forbidding the disclosure of details about the drugs and their manufacturers.
Twice this year, the Supreme Court has turned away appeals seeking to block an execution on the grounds the condemned inmate and his lawyer had a right to know more about the drugs to be used in a lethal injection. But in late February, three justices — Ruth Bader Ginsburg, Sonia Sotomayor and Elena Kagan — dissented in a Missouri case and said they would have stopped the execution.
Lawyers said they feared their client would suffer searing pain from chemicals if he was not properly sedated. They pointed to a series of recent executions that went badly, according to observers.
On Jan. 9, an Oklahoma inmate, Michael Lee Wilson, reportedly said, "I feel my whole body burning" after he was injected with a compounded pentobarbital. On Jan. 16, an Ohio inmate, Dennis McGuire, took more than 20 minutes to die, and observers said he was struggling and gasping for air.
In the case of Lockett and another Oklahoma inmate, Charles F. Warner, 46, who had also been scheduled for execution Tuesday, state officials provided assurances in court that their lethal-injection methods had "been vetted and approved by federal courts in various jurisdictions."
The botched execution, experts and death penalty opponents said, has substantially damaged the credibility of those officials' arguments and possibly even similar arguments for officials in other states.
"I can't imagine a bigger debacle for the state of Oklahoma," said Johnson, the Democratic state senator and death penalty opponent whose brother was murdered in 1981.
Legal analysts said the lack of public disclosure on the ingredients in lethal injections could provide a basis for new federal appeals.
"This is a very conservative Supreme Court, but after this, I can easily see them saying the states need to reveal more," said Cornell University law professor John Blume, who directs a legal clinic that provides representation in death penalty cases.
The American Civil Liberties Union of Oklahoma is arguing that even if the Supreme Court expressly rules that new lethal-injection drugs are constitutional, a case could be made that concealing the means of execution could in itself represent cruel and unusual punishment — particularly after this week's incident.
"We have a real injury here now — a person is dead and it appears he was tortured," said Ryan Kiesel, the group's executive director. "It's no longer speculative that the lack of transparency causes harm. So the courts will have an opportunity to consider the issue, if they take it."
Fallin said Wednesday that she had ordered an independent review into the state's execution policies and the cause of Lockett's death, but opponents quickly questioned the governor's decision to appoint her own commissioner for the Oklahoma Department of Public Safety to lead the review, in conjunction with investigators from the state attorney general's office.
Whether state officials will pursue further executions in Oklahoma is unclear. Warner received a two-week reprieve, which his attorney called insufficient.
"The idea that this review process can be completed in two weeks is ludicrous, and it's terribly unfair to have Mr. Warner and his family in a two-week holding pattern," said Warner's attorney, Madeline Cohen. "No execution should take place until there is a full accounting of what happened and complete transparency in the execution process."
Hennessy-Fiske reported from Oklahoma City, Pearce from Los Angeles and Savage from Washington.