Yesterday's decision to overturn the conviction of a terminally-ill man held in solitary confinement in the USA for more than 41 years after a flawed trial is a positive step but long overdue after four decades of injustice, Amnesty International said.

Herman Wallace, 71, was placed in solitary confinement in Louisiana State prison after the murder of a prison guard, Brent Miller, in 1972. In 1974 Wallace was convicted of Miller's murder, while a fellow prisoner - Albert Woodfox - was also convicted of this murder in 1973.

USA Campaigner at Amnesty International, Tessa Murphy, said:

“The case of Herman Wallace is a tragic example of ‘justice’ gone wrong in the USA. Finally a federal court has acknowledged some of the unfairness surrounding this case. However this sadly comes too late for lasting benefit as he is at death’s door with terminal cancer.

“The state must not now try to block his release.”

Yesterday's ruling focused on one aspect of his trial: the systematic exclusion of women from the grand jury. Many other irregularities have been raised over the years but have been rejected by the state courts.

No physical evidence linked Wallace to the crime. It was later revealed that a key prosecution witness received favours, including a pardon, in return for his testimony in the case.

Immediately following the murder, Wallace was placed in solitary confinement in a cell measuring two by three metres and was confined in this tiny space for 23 hours a day. Kept in these conditions for more than four decades, he was denied access to meaningful social interaction, work opportunities, education and rehabilitation programmes.

Throughout this period he was only allowed out of his cell for seven hours a week, which he would spend showering or in solitary recreation.

Amnesty International knows of only one other person in the USA who has been held for longer under such harsh conditions.

More than 160 times since 1972, the prison review board has considered and reaffirmed the original decision to keep Wallace in lockdown. These reviews have failed to meet due process standards which would have required his behaviour to be re-evaluated at regular intervals to determine whether confinement was still warranted.

Wallace is one of the so-called Angola Three. The other members are Robert Hilary King and Albert Woodfox.

Wallace and Woodfox, who was convicted of the same crime, have consistently maintained their innocence in the murder of Brent Miller and claimed they were falsely implicated for their political activism in prison as members of the Black Panther Party.

King, who was a co-founder of the Black Panther Party along with Wallace and Woodfox, was convicted of a different crime and released after 29 years of solitary confinement.

The ruling may be encouraging for Woodfox, who remains in solitary confinement and has a similar appeal pending before the federal court.

• Read more about our work on the Angola 3