One hears many disturbing accounts of death penalty cases in the USA. Only recently the execution of Troy Davis in Georgia attracted worldwide attention. But to meet in person someone who has been on Death Row and come out alive adds something to the picture that little else could. Thus a sizeable audience was held in rapt attention by the event yesterday evening at Drumsheugh Gardens, where the support charity Amicus introduced us to Lane Nelson.

Unlike Davis, Nelson does not deny his responsibility for the death with which he was charged, when as a young hitchhiker in Louisiana in 1981, with a drink and drug problem, he ended up fatally stabbing a driver who offered him a lift. But there were strange circumstances, and a factor present that mirrors the comment of one Supreme Court justice that "I have yet to see a death case [among the dozens coming before the court on stay-of-execution applications] in which the defendant was well represented".

That apart, there are many other disturbing features of such cases. Nelson first arrived in Louisiana's Death Row in 1986. There are at least five men still there, he says, who were already there before him. Currently, the state isn't pushing for executions. There was one last year - of someone who actually asked for the sentence to be carried out. Before that, the last was in 2001 or 2002, though Nelson went through one summer when eight fellow inmates were put to death in 11 weeks.

Yet prisoners are kept in cells only 9ft by 6ft (including bed, sink and toilet), where they are confined 23 hours a day (and allowed out of doors three times a week). Such contact as takes place with visitors, including family members, is through a thick screen which barely permits you to see the other person. People go mad there, Nelson said. He could have done, but kept his "survival tools". He doesn't think he would have committed suicide, "but it was comforting to think I had the option".

And the fate of prisoners seems arbitrary. Nelson saw a man reprieved who had kidnapped, raped and murdered a three year old girl; another was not, for a death caused by a single stab wound in the course of a robbery.

In his own case a successful appeal led to his sentence being commuted to life without parole. Years later he successfully applied for clemency, and he was finally released early this year, 30 years after his initial arrest.

What seems to come through regularly in Death Row cases, apart from the inadequacy of court-appointed defence representation, is the question marks over the prosecution case, and perhaps the consequences of a more politicised justice system, with pressure on prosecutors to secure convictions. And that's before you start on the race statistics which point to a far greater likelihood of a capital penalty if your victim is white than if they are black; as well as a higher proportion of blacks among those actually executed.

But for organisations like Amicus, and those they support, one ray of hope is the statistic that since 1973, 138 people in 26 states have been released from Death Row with evidence of their innocence. And some states are more reluctant these days to actually carry out the sentence, though no one expects an early end to the practice nationwide.

For those who can only watch from a distance, there is the option of financially supporting the likes of Amicus, or Clive Stafford Smith's Reprieve. There is also the possibility of moral support for individual prisoners through "pen pal" type correspondence: Andrew Lee Jones, a young black executed in 1991, in whose memory Amicus was founded, was befriended from a distance by an English woman, Jane. Her letters to him have not survived, but his letters to her have been collected and published, and extracts were read at this week's event. They are moving, poignant, and eloquent of the humanity of those involved. Enough, in itself, to question the morality of insisting on the availability of the sentence, and all the more so on carrying it out perhaps many years after the offence.