"The gallows is not only a machine of death but a symbol. It is the symbol of terror, cruelty and irreverence for life, the common denominator of primitive savagery, medieval fanaticism and modern totalitarianism"
- Arthur Koestler

After close to 21 years on death row in Ohio, Kenny Richey flew into Scotland yesterday to hug his mum, lie on his back in the grass, gaze into the big sky, feel the wind in what's left of his hair and start his life all over again. "Walking free is the dream that's kept me going," he said after his release on Monday following what Amnesty International has described as "one of the most compelling miscarriages of justice" ever recorded. At one point, he came within an hour of being sent to the electric chair and continued to face the threat of execution for the aggravated murder of a toddler who died in a 1986 fire because the prosecution refused to acknowledge that the scientific testimony offered at his trial was false and unreliable. He has always maintained his innocence. (The fire was probably due to a cigarette end left smouldering on a settee.) Campaigners such as Clive Stafford Smith, of the lobby group Reprieve, who has defended scores of US death row and Guantanamo inmates, notices an interesting dichotomy in his postbag. Most of the letters from Britain cheer him on, while hate mail, including death threats, invariably comes from Americans.

It was the obscenity of the hanging of Timothy Evans, an innocent man, in 1949 that mustered British public opinion and led to a moratorium on the death penalty in 1965 and abolition four years later. But in the US, particularly the deep South, state killing is alive and well. As 80% of victims in capital cases are white and a disproportionate number of inmates are black, some put it down to systemic racism. Stafford Smith thinks it's more about hate. "People there are inspired to hate small groups to distract them from the real problems of life," he once said.

Support for executions fell to an all-time low in the 1960s after European countries began to abolish them but following a 10-year moratorium, murderer Gary Gilmore was executed by firing squad in Utah in 1977 and, since then, more than 1000 men and women have followed him. Of the 36 states that retain the death penalty, 10 still use it and there are currently 3350 people awaiting execution.

Americans share their enthusiasm for the unique horror of judicial killings with some strange bedfellows. An eye-catching Amnesty International poster from the early 1990s depicted a number of world leaders, each with his hand in the air: Adolf Hitler, Joseph Stalin, Mao, Idi Amin, Saddam Hussein and the then US President, George Bush Sr. The caption read: "All those in favour of the death penalty, raise your hand". Like father, like son. As governor of Texas between 1995 and 2001, George W Bush authorised a record 152 executions, including cases where there were severe doubts about the safety of the conviction and strong mitigating circumstances. It is true that in the judicial killing stakes, the US is outdone by Iran and China, but what's so shocking is that this is the country that claims to represent the gold standard for liberty and democracy. It doesn't seem to fit Koestler's definition.

Yet it chooses to incarcerate 1.7 million people and between half and two-thirds of citizens still back the death penalty. There is a distasteful debate going on about whether lethal injections with a three-drug cocktail, the procedure most commonly used in the US, constitutes a "cruel and unusual punishment". Excuse me? A process that can paralyse, while failing to anaesthetise, leaving prisoners to die in unimaginable agony, while unable to cry for help? The use of a drug that under Texas law is prohibited for vets putting dogs and cats to sleep?

Cruel and unusual punishment seems something of an understatement, doesn't it? But don't expect the Supreme Court's recent decision to examine the constitutionality of the three-drug cocktail to end the death penalty in the US. Already, individual states are working on different witches' brews that they claim will kill more efficiently.

Meanwhile, not one of the main candidates for the presidency, Democrat or Republican, is prepared to stand up for abolition. Barack Obama said he was against the death penalty when he was running for office in Illinois but has now backtracked. Hillary Clinton says she is against executing people with low IQs, following a string of shocking cases, but it has now been made illegal anyway. "In short, nobody wants to go near the issue," said a spokeswoman for Reprieve yesterday.

The main argument for supporting state killings is that it acts as a deterrent, despite ample evidence to the contrary. In Canada, the murder rate declined sharply after abolition, while in the US its survival appears to have a brutalising effect on society, resulting in more violence. It is also clearly arbitrary and unfair in a number of respects. Around 95% of death-row inmates can't afford their own lawyers, and court-appointed attorneys often lack the relevant experience. And because it is up to each prosecutor to decide whether or not to seek the death penalty, plea bargaining, local politics and pure chance make a lottery of who lives or dies, with the dice stacked most heavily against a black southerner accused of killing someone who is white.

A few years ago I sat in on just such a trial in Dallas. What was striking was the lackadaisical attitude of the defence and the judge, who spent most of the afternoon with his cowboy-booted feet crossed on the desk in front of him.

Americans are growing more sensitive to the fallibility of their judicial system. The advent of DNA testing and its use to overturn death sentences has raised the profile of the issue. But abolitionists are nervous of putting too much faith in it because it can act just as easily against them, helping to secure a guilty verdict.

Besides, I'm not only opposed to the death penalty because of its potential for killing innocent people. I don't want the guilty killed either. Surely human rights apply to the worst as well as the best of us. That is why they protect us all. Some question AI's campaign against capital punishment, arguing that it taints its work on behalf of prisoners of conscience. But the right to life is the most basic human right of all. When the state executes a criminal, its action merely mimics the criminal's willingness to use physical violence against a victim.

The British cannot afford to be smug in this debate, after years in which little was done to get Kenny Richey home and with several other British nationals still on death row, including Linda Carty in Texas, convicted of a neighbour's murder after a mockery of a trial.

Besides, the argument that someone "deserves" to die is morally indistinguishable from saying that someone "deserves" to be imprisoned without charge. A Prime Minister who claims that human rights are universal has no business to be supporting the idea of locking up suspects for six weeks without even telling them why they are there.