It did not emerge because the judges asked specifically to hear about the evidence of Dr Michael Unsworth-White, the only witness to place the sisters at the scene of the crime at the material time; the non-disclosure of statements; and the role of the press.
However, Ann and Derek Taylor, who campaigned tirelessly for their daughters, privately commissioned a report from the respected Home Office pathologist, Dr A C 'Bill' Hunt, who concluded that 'an attack by a male intruder seens by far the most likely explanation of the death of Mrs Shaughnessy'.
In their judgment, the appeal court judges, Lord Justice McCowan, Mr Justice Tuckey and Mr Justice Douglas Brown, criticised the police and the press. The case raises questions about the adequacy of supervision by the Crown Prosecution Service and the conduct of professional and lay witnesses.
At the trial, the Crown pathologist, Professor Rufus Crompton, said that Mrs Shaughnessy's wounds were likely to have been inflicted by a woman. 'It would suggest the capability of a female,' he said. Under cross-examination, though, he conceded he was unable to determine the sex of the attacker. But the concession followed wide reporting of his earlier remarks.
The report by Dr Hunt, who has made a special study of injuries inflicted by stabbing, makes clear that the entire prosecution was misconceived. 'It appears that an assailant held one hand over the mouth from behind and inflicted the fatal injuries with a knife in the other hand,' he concluded. 'There is no evidence that more than one person was involved . . . I would have expected the assailant to have bloodstains upon his or her clothing.' There was no forensic evidence against the Taylor sisters.
Dr Hunt added that his experience of stabbing cases 'does not exclude the possibility that Mrs Shaughnessy was killed by a woman', but 'it does make it unlikely'. He added: 'It would be easy for a fairly tall person to inflict the injuries . . . it seems impossible for an individual of the same height (5ft 3in) as the deceased to inflict them. I have been informed that both Lisa and Michelle are only 5ft 2in tall and, in my view, this must exclude either of them.'
In the non-disclosed material, lawyers for the Taylors also found a statement from a man questioned a day after the murder in the road where it happened, in Battersea, south London.
He said he was unable to 'recall any unusual events at the relevant time except a green Cortina estate, about T-registration, parked at the end of the road blocking traffic at about 6pm.'
Two months later, within days of the Taylors' arrest, the same man said in a statement that he had noticed the car at 5.35pm and that it was a 'white estate car - I am sure a Ford Sierra'.
His evidence had thus changed in four vital respects - each of which fitted the prosecution case. Michelle Taylor drove a white Sierra estate. Michelle and Lisa can now celebrate their release, while regretting the time that was wasted in prison. The living-room floor of their house in Forest Hill, south London, is strewn with flowers and copies of newspapers, now telling a very different story about them.
'The girls still don't feel justice has been done,' said Ann Taylor. 'They have ben protesting their innocence from the beginning. After the verdict, the police told the press that Michelle and Lisa were wicked, evil girls, but all along they were withholding the evidence which proved their innocence.
'We want the case reopened now, not because of the girls themselves but because of everyone else involved, including Alison's family and especially her parents - what must they be going through now?'
But the questions raised by the sisters' long ordeal have been posed too late to be considered by the Royal Commission on the criminal justice system, which will deliver its long-awaited report early next month.