A severe shortage of lethal injection drugs, and the horribly botched execution of a convicted murderer in Oklahoma, have brought the debate over the death penalty in the US back to the fore, once again.
During his execution by lethal injection on the evening of 29 April, Clayton Lockett, 38, writhed and gasped on the gurney several minutes after a doctor had declared him unconscious. The execution was halted, only for Lockett to die of a heart attack shortly afterwards.
Last Thursday, the Supreme Court stayed the execution by lethal injection of a Missouri death row inmate, 46-year-old Russell Bucklew, after lawyers claimed that he, too, could suffer a painful and prolonged death. On the same day, in Tennessee, the Republican governor, Bill Haslam, signed a law reinstating electrocution as a method of execution, if the necessary drugs for a lethal injection cannot be obtained. The law was passed by large majorities in the state's upper and lower houses.
The drugs used in lethal injections have become increasingly scarce after the EU introduced a sweeping ban on their export to death-penalty states in the US. The ban and subsequent shortage has significantly slowed the rate of executions, but it has also led states to consider other methods of execution – and to experiment with untested drug combinations, often made up of drugs from unidentified and largely unregulated "compounding pharmacies", which mix small batches for specific purposes.
Long considered the most humane form of capital punishment, lethal injection has come under scrutiny following several troubling incidents. During his execution by lethal injection in Oklahoma, in January, 38-year-old Michael Wilson's reported last words were: "I feel my whole body burning." In Ohio, in the same month, Dennis McGuire, 53, snorted and gasped repeatedly during the 26 minutes it took him to die. Oklahoma officials said Lockett's execution was bungled because the inmate's vein collapsed during the injection.
In pictures: Controversial executions
In pictures: Controversial executions
1/5 Clayton Lockett, 38
Convicted of the murder and rape of 19-year-old Stephanie Neiman in 2000 and sentenced to death. Lockett died of a heart attack after a failed execution by lethal injection in April.
2/5 Roy Blankenship, 55
Killed by lethal injection in 2011 after he murdered an elderly woman. Witnesses saw him grimace and jerk as he became the first person put to death in that state with pentobarbital. Medical experts said he “suffered greatly”.
3/5 Michael Wilson, 38
Executed by lethal injection in January. Wilson was convicted of murdering co-worker Richard Yost during a robbery at a convenience store in 1995. He is one of three people executed for the crime.
4/5 Dennis McGuire, 53
Sentenced to death following the rape and murder of pregnant 22-year-old Joy Stewart in 1989. After spending 25 years on death row fighting the order to end his life, McGuire was executed by lethal injection in January.
5/5 George Stinney Jr, 14
George Stinney Jr became the youngest person to be executed in the US in the 20th century when he was sent to the electric chair in 1944 during the trial that lasted less than three hours and reportedly bore no evidence and barely any witness testimonies.
There have been no executions carried out by any US state since Lockett's shocking demise, but Bucklew's last-minute reprieve marked the second time in as many weeks that a death row prisoner had his lethal injection postponed. Convicted murderer Robert Campbell had been due to die in Texas on 13 May, but a court halted it at the 11th hour.
Though the Supreme Court did not detail its reasons for delaying Bucklew's execution, many observers believe the Lockett case was instrumental in the ruling. "It was surely on their minds," said Richard Dieter, the president of the Death Penalty Information Centre. "The Lockett case has had a noticeable effect: executions have been stayed, and now states are edging away from lethal injection."
The complications now surrounding the application of lethal injection have reportedly prompted a Wyoming legislative committee to draft a bill calling for the reintroduction of the firing squad.
In Utah, where Representative Paul Ray, a Republican, hopes to introduce a similar proposal, the last execution by firing squad occurred as recently as 2010. The practice was discontinued in 2004, but those sentenced to death before then could still choose it as an alternative.
In Louisiana, the prisons chief James LeBlanc recently suggested that the state consider nitrogen asphyxiation as a more reliably "humane" method than lethal injection. The last gas chamber execution in the US took place in 1999.
Professor Deborah Denno, an expert on execution methods at the Fordham University Law School in New York, said: "There is a contingent that believes we will eventually find a perfect method of execution … [but] in a lot of cases, it's nothing to do with the drugs. It's to do with the executioners' incompetence."
Overall, the death penalty remains in 32 US states, though only 10 have carried out executions in recent years. US courts imposed 80 death sentences last year, down from 315 in 1994. There were 39 executions in 2013, compared to 98 in 1999.
"The shortage of lethal injection drugs is another nail in the coffin of the death penalty," said Mr Dieter. "In people's minds, the death penalty is now associated with executing the innocent and botched executions."
Method of dispatch
Lethal injection The primary method of execution used by all 32 states that still have the death penalty. There have been more than 1,200 executions using injections since 1976. Sodium thiopental puts inmates to sleep followed by potassium chloride which stops the heart.
Electrocution Eight US states still use the electric chair. First built in 1888, prisoners are blindfolded and then given a 30-second jolt of electricity between 500 and 2,000 volts.
Gas chamber Introduced in 1924, and still used in Arizona, Missouri and Wyoming. This method uses hydrogen cyanide gas delivered into a chamber. The prisoner dies from hypoxia, the cutting-off of oxygen to the brain.
Hanging The primary execution method in the US until the 1890s. Three prisoners have been executed by hanging since 1976 and it is still authorised in Delaware, New Hampshire and Washington.
Firing squad Remains a method of execution in Utah if chosen by a prisoner sentenced before 2004.