A killer on death row in the US state of Missouri has no right to a "painless death", the US Supreme Court has ruled.
Russell Bucklew was convicted of murder, kidnap and rape in 1996.
The 50-year-old suffers from a disease called cavernous hemangioma - which causes vascular tumours to grow in his head, neck and throat.
His complaint alleged this condition could prevent the drug used for killing him, pentobarbital, from circulating properly in his body.
He also claimed that the use of a chemical dye to flush the intravenous line could cause his blood pressure to spike and his tumours to rupture - and that the pentobarbital could "adversely" interact with his other medications.
His lawyers said the death penalty was in violation of the US Constitution's Eighth Amendment, which bars cruel and unusual punishment.
But the judges ruled 5-4 against his appeal, and said he had failed to present enough evidence for them to grant his request to be executed by lethal gas instead.
In its judgement, the court said: "His suit in the end amounts to little more than an attack on settled precedent, lacking enough evidence even to survive summary judgment - and on not just one but many essential legal elements set forth in our case law and required by the Constitution's original meaning."
Bucklew had sought to be put to death by an alternative method that would "significantly reduce a substantial risk of severe pain".
The judges said: "Bucklew has provided evidence of a serious risk that his execution will be excruciating and grotesque. The majority holds that the State may execute him anyway."
Justice Neil Gorsuch wrote: "The Eighth Amendment does not guarantee a prisoner a painless death - something that, of course, isn't guaranteed to many people, including most victims of capital crimes."
The judge, who was appointed by President Donald Trump in 2017, also noted: "Mr Bucklew committed his crimes more than two decades ago.
"He exhausted his appeal and separate state and federal habeas challenges more than a decade ago.
"Yet since then he has managed to secure delay through lawsuit after lawsuit."
He filed his current challenge just days before his scheduled execution.
That suit has been on-going for five years and yielded two appeals, two 11th-hour stays of execution and plenary consideration in the Supreme Court.
Judge Gorsuch added: "The people of Missouri, the surviving victims of Mr Bucklew's crimes, and others like them deserve better."