The 38-year-old prisoner, Troy Kunkle, who is on death row in Texas having been convicted of a murder committed in 1984, is set to be executed on 25 January. The state authorities are relying on a legal technicality to push ahead with the execution.

Kunkle’s death sentence was imposed without the original jury being asked to consider any mitigating evidence - a process later deemed unconstitutional in a legal change.

The jury also never heard any expert mental health evidence. Since his conviction evaluations have indicated that Kunkle suffers from serious mental illness, including schizophrenia.

Kunkle, who had no criminal record before the killing, had an abusive upbringing. When he was 12 his father’s mental health deteriorated and he was subject to extremely violent attacks from his father.

Attacks included his father slamming his head into walls and putting Kunkle into life-threatening chokeholds. His mother also suffered from serious mental illness and Kunkle’s childhood was scarred by violence and neglect.

A psychologist has concluded that an expert evaluation at the time of the trial would have been likely to have shown Kunkle’s emerging mental disorder.

Several of the jurors in his case have since indicated that they would have voted for life imprisonment if they had been allowed to give weight to mitigating evidence.

In December the US Supreme Court expressed "regret" that despite Kunkle’s sentence being "imposed in violation of the Constitution", it was unable to act because Texas had relied on a technical rule that prevents federal courts intervening on procedural matters.

Amnesty International UK Director Kate Allen:

"It is clearly wrong that Texas should rely on a legal technicality to push ahead with the execution of man whose history of childhood abuse and mental illness was never properly considered at his trial.

"The Texas paroles board should recommend that the state governor commute Troy’s sentence and failing that the governor should use his power to commute the sentence.

"We wish to see the total abolition of the death penalty and this disgraceful case is just one of the reasons why."

In November the Supreme Court stayed Kunkle’s execution less than an hour before it was due to be carried out. Earlier in 2004 a legal decision had allowed several Texas death row prisoners to apply for new sentencing hearings to address the question of mitigating evidence not being considered by juries at their original trial convictions.

Kunkle is being denied a new sentencing hearing on the basis that Texas court rules prevent inmates from repeat-filing a claim already lost, even though this had only been lost because of a longstanding misapplication of the law.

Kate Allen added:

"Texas is relying on a bizarrely rigid application of the letter of the law to press ahead with Kunkle’s execution. It should now show that it understands the spirit of the law and allow Kunkle his constitutional rights. His execution would be a travesty, bringing nothing but shame on Texas."

Executions in Texas constitute more than one-third of the total number of executions carried out in the USA – 337 out of 946 – since 1977. Many of these have been carried out in contravention of international standards.