The Appeal Court in London will decide tomorrow whether to release, or order the retrial of, a man serving a life sentence for the murders of a mother and daughter, Lin and Megan Russell, and the attempted murder of another daughter, Josie, in 1996.
In a dramatic development, three judges at the appeal court yesterday said Michael Stone's appeal against his conviction for the murders "must succeed" after the prosecution conceded that a key witness who gave evidence against Stone that he had confessed to the murders had been "completely discredited".
On the second day of the appeal hearing the prosecution indicated that, having considered all the material available to the court, it could no longer rely on Mr Barry Thompson "as a witness of truth".
The prosecution added that Mr Thompson would not have been called to give evidence at Stone's trial at Maidstone Crown Court in 1998 if it had been aware at the time of the material now available.
Lord Justice Kennedy, sitting with Mr Justice Kay and Mrs Justice Hallett, did not formally quash Stone's conviction. But tomorrow they will consider the prosecution's application for a retrial.
Stone's lawyers have indicated that they will oppose the application. If they are successful, he will be freed.
Stone was convicted of murdering Lin and Megan Russell, and of attempting to murder Josie Russell, as Mrs Russell and her daughters walked to their home in Chillenden, near Kent.
Josie, who was badly injured in the attack, which was probably carried out with a hammer, received emergency surgery in the neurological unit of King's College Hospital, London.
She was left for dead with a hole the size of an apple in her skull. She survived, however, and her evidence was painstakingly recorded by police officers over several months of interviews.
It is unlikely that Josie will ever fully recover from her injuries. After the attack she had to learn to speak again and had to undergo major surgery to cover the hole in her skull with a metal plate.
While Stone was on remand in Canterbury prison a fellow prisoner claimed he had confessed to the murders to a third prisoner, Damien Daly.
However, just days after Stone's conviction Thompson was reported as saying that he had told the jury "a pack of lies". In subsequent newspaper interviews Thompson claimed that he and another prosecution witness were "paid police informants".
Thompson's evidence was described by Stone's counsel, Mr William Clegg QC, as a "supporting echo" of Daley's claim that he had confessed to the murders. But Mr Clegg told the appeal court that police had found no forensic evidence linking Stone to the murders, and that he continued to deny carrying them out.
On hearing yesterday's decision Stone turned to his sister Barbara and smiled, and she then punched the air in delight.