All Wilbert Rideau needed to do for four decades as an inmate in one of America's harshest prisons - the Angola State Penitentiary in Louisiana - was to keep his head down.

But that isn't his style. Instead Rideau, incarcerated in 1961 for murder, took precisely the wrong path. He turned himself into a model prisoner.

His "mistakes" have ranged from editing the prison magazine, The Angolite, to writing books, lecturing and co-producing an Oscar-nominated film about life behind bars. In the process, he has earned some of the highest accolades in US journalism.

ABC News once named him "Person of the Week". In Life magazine he was "The Most Rehabilitated Prisoner in America".

Amazing feats these may be for a man who was 19 years old and barely educated when he first went inside. But today, Rideau, now 63, has the poise and glint-in-the-eye of a man with intact self-respect and admits that although his feats have earned him the admiration of people around the country, they may also have cost him the one prize every prisoner craves: freedom.

That is because there are others in the country - and especially in southwest Louisiana - who do not care for Rideau one bit. Rather than being impressed by his deeds, they become increasingly infuriated by them. Just as his supporters say it is time to let him go, these other folk, many of them powerful, wish to see him rot and die inside his cell.

It is a battle that may soon be resolved. What is happening in the long saga of Rideau's confinement is unprecedented in US judicial history. The model prisoner went on trial this week for the fourth time over the killing of a young woman more than 40 years ago.

This is not a story about a black man wrongfully convicted and locked up for a crime he never committed. True, at the new trial which opened on Monday, Rideau pleaded not guilty, but that is how the system works.

Rideau's crime dates from February 1961 when he was 19. Having robbed a bank in the small town of Lake Charles, he took three bank employees hostage and drove them to a remote bayou before shooting them. The bank manager was hit in the arm but managed to flee, another woman was shot in the neck but lay still feigning death. Rideau stabbed the third, Julia Ferguson, in the heart and then slit her throat.

Rideau has never denied killing Ferguson but his defence lawyers argue his behaviour was the act of a rash teenager caught up in a robbery that had gone wrong.

When the case opened for the fourth time in Lake Charles on Monday, his lawyers urged the jury to convict him of manslaughter, not murder.

"Let me tell you right now," one of Rideau's lawyers, George Kendall, admitted to the jury. "Mr Rideau is responsible for the death of Julia Ferguson." But: "You will see these are not the acts of a well-conceived plan to eliminate witnesses but the impulsive acts of a nervous and confused man."