An inmate in the US state of Arizona took almost two hours to die by lethal injection in the latest botched execution to raise questions about the death penalty in the United States.
The execution of convicted double murderer Joseph Wood began at 1.52pm (local time) yesterday at a state prison complex.
The 55-year-old was pronounced dead just shy of two hours later at 3.49pm, the Arizona attorney general's office said.
During that time, his lawyers filed an unsuccessful emergency appeal to multiple federal courts that sought to have the execution halted and their client given life-saving medical treatment.
The appeal said the procedure violated his constitutional right to be executed without suffering cruel and unusual punishment.
It was denied by Justice Anthony Kennedy of the US Supreme Court.
"He gasped and struggled to breathe for about an hour and 40 minutes," said one of Wood's attorneys, Dale Baich.
"Arizona appears to have joined several other states who have been responsible for an entirely preventable horror: a bungled execution. The public should hold its officials responsible."
Arizona Governor Jan Brewer expressed concern over how long the procedure took.
He ordered the state's Department of Corrections to conduct a full review, but said justice had been done and that the execution was lawful.
"One thing is certain, however, inmate Wood died in a lawful manner and by eyewitness and medical accounts he did not suffer," the Republican governor said in a statement.
"This is in stark comparison to the gruesome, vicious suffering that he inflicted on his two victims, and the lifetime of suffering he has caused their family."
An Arizona Republic journalist who witnessed the execution said he counted the inmate gasping for breath about 660 times.
"I just know it was not efficient," said the reporter, Michael Kiefer. "It took a long time."
Charles Ryan, director of Arizona's Department of Corrections, said protocol was followed and that the execution was monitored by a team of licensed medical professionals.
He said Wood was "fully and deeply sedated" five minutes after the drugs began to be administered.
He said that the medical team reaffirmed that he remained deeply sedated seven more times before he was pronounced dead.
Mr Ryan said in a statement that apart from snoring, Wood "did not grimace or make any further movement".
The Pima County Medical Examiner will conduct an independent autopsy, he said, and a toxicology study was requested too.
Wood had been one of six death row prisoners who sued Arizona last month arguing that secrecy surrounding the drugs used in other botched executions in Ohio and Oklahoma violated their rights.
But he exhausted his appeals yesterday when the Arizona Supreme Court lifted a hold after reviewing a last-minute appeal that involved demands for more information about the lethal drug cocktail to be used in the execution.
Wood's lawyers had also wanted to know the qualifications of the medical staff conducting the execution.
Anti-death penalty campaigners expressed horror over the drawn-out death.
Cassandra Stubbs, director of the American Civil Liberties Union's Capital Punishment Project, said Arizona had broken constitutional rights, and the bounds of basic decency.
"It's time for Arizona and the other states still using lethal injection to admit that this experiment with unreliable drugs is a failure," she said in a statement.
Diann Rust-Tierney, executive director of the National Coalition to Abolish the Death Penalty, said Wood's execution had been shocking, cruel and entirely predictable.
"Americans have had enough of the barbarism," she said.
In January, convicted rapist and murderer Dennis McGuire was put to death in Ohio using a sedative-painkiller mix of midazolam and hydromorphone, the first such combination administered for a lethal injection in the US.
The execution took about 25 minutes to complete, with McGuire reportedly convulsing and gasping for breath.
In Oklahoma in April, convicted killer Clayton Lockett writhed in pain and a needle became dislodged during his lethal injection at a state prison.
The execution was halted, but Lockett died about 30 minutes later of a heart attack.