The Court of Appeal has quashed the convictions of two men for a catalogue of sexual abuse against relatives in a small village more than 30 years ago.
Judges ruled the trial jury in 2004 were not given adequate directions.
Lord Justice Higgins said the summing up did not refer to the defence's difficulties in providing alibis when so much time had passed.
A hearing will take place next month to decide if the two men, who cannot be identified, should face a retrial.
The pair, now aged 48 and 50, were convicted of a series of charges including indecent assault, gross indecency and buggery.
The alleged offences spanned from 1973 to 1995, with the defendants accused of beginning the abuse in their teens.
They appealed the guilty verdict on a number of grounds, including insufficient directions being given to jurors deciding an historic sex abuse case.
'Frailty of human memory'
Lord Justice Higgins, sitting with Lord Justices Girvan and Coghlin, acknowledged the trial judge faced "an unenviable task" in circumstances where the accused may struggle to produce an alibi for offences allegedly committed on unspecified dates many years previously.
"The means to secure a fair trial for an accused faced with historic allegations lie in careful directions to the jury which expose the difficulties created for accused persons and at the same time to remind the jury of the frailty of human memory in the context of the particular allegations made and the time frame concerned," he said.
Lord Justice Higgins said in the summing up at the original trial, there was no reference to the difficulty of producing alibi evidence "nor were the jury asked to reflect on the effect of the passage of time on the reliability of the evidence of any of the witnesses".
He added that nowhere did the trial judge allude to the problems created for the defendants in countering allegations from many years ago.
"Crucially he did not refer to the further difficulty for the applicants that the exact date was unknown and that the events were alleged to have occurred between dates spanning many months or longer," he said.
Lord Justice Higgins ruled that some reference should have been made to the difficulties for defendants facing sexual abuse claims many years in the past.
"The way the matter was left with the jury was that either the allegations were true or false," he said.
"While in one sense that was correct, it overlooked the question whether the recollections of the complainants... were accurate and reliable."