James Allridge is an unusual sort of artist. His work has been exhibited in New York, Washington and Switzerland, and yet he has never been present for one of his own openings. He has a lively correspondence with dozens of friends around the world, including the Hollywood actress Susan Sarandon, but he never visits them and they hardly ever come to see him.

The reason? He is a prisoner on Texas's death row, who faces execution by lethal injection later this month unless he can convince the state's notoriously reluctant Board of Pardons and Paroles to recommend commuting his sentence. Allridge's many friends argue that he is a model prisoner, who has been completely rehabilitated following the brutal murder he committed at a Forth Worth convenience store in 1985.

Four of the jurors at his original trial agree, as do a number of the prison guards who have watched over him. They say that he is such a calming influence at the Polunsky Unit in Livington, where Texas's death row inmates are housed, that he has almost certainly saved lives.

The question is, will this be enough in the state that carries out more executions than any other place in the Western world? "Executing people like James sends a message that there is no point rehabilitating people and turning them into positive members of the prison community," says his lawyer, Jim Marcus of the Texas Defender Service.

This is an unusual case in every respect. Prison in the United States - with its notorious culture of systemised rape, terrifying spasms of physical violence, endemic racism and drug use - can turn the gentlest of creatures into either a monster or a psychic wreck. Allridge, by contrast, has a strikingly clean record. The last time he was written up for failing to obey prison staff was 15 years ago. He had two fights in his first two years inside, and in both cases he was written up as the victim, not the instigator.

"He has spent his time focused on trying to better himself," Mr Marcus said. "He enrolled in educational classes, did his artwork and produced newsletters. More recently, he has also worked as a counsellor to younger death row inmates."

And one of his guards, Jacoby Garmon, wrote in an affidavit to the parole board: "I would consider James a role model prisoner. [He] probably saved a lot of correctional officers' lives and they didn't even know it, just by calming the situation."

Not everyone supports the commutation, starting with the family of the victim, Brian Clendennen, who was 21 when Allridge shot him dead in a robbery that netted $300 (£163). The jury at Allridge's trial was never asked, however, whether they thought he deserved to die. Instead, they were asked whether they felt he could pose a future danger to others - a prerequisite for the death penalty in Texas.

His lawyers and friends argue that the crime was committed under the influence of his brother Ronald, who was executed in 1995, and that all indications now suggest he would never do such a thing again. Susan Sarandon, who has corresponded with him for seven years, quietly slipped in to see him last week to offer her support.

Allridge's art is very far from the usual prison-house themes of incarceration and social injustice. He specialises in detailed drawings of flowers in bright colours and other images clearly inspired by life on the outside.

The clemency petition, filed last week, offers the Texas authorities two choices: commutation to life imprisonment, or a six-month postponement of the execution. The point of the latter is that the Texas legislature is due to meet in January and is considering cleaning up some of the more egregious aspects of the state's system of capital punishment. One of the reforms could be to force the Board of Pardons and Paroles to hold formal hearings, rather than reaching their conclusions by sending faxes to each other from their homes.