A former village postmistress sentenced to 18 months in jail is one of 34 people whose convictions are being reviewed.
It comes after former subpostmasters who brought legal action against the Post Office have hailed a victory as a High Court dispute formally came to an end.
Jacqueline McDonald, who ran the post office in Broughton, saw her life fall apart after she was jailed for false accounting and stealing almost £100,000 in January 2011. She spent four and a half months in prison.
But Mr Justice Fraser, who presided over the High Court case, approved a £58 million settlement - announced last week - between the Post Office and more than 550 claimants at a hearing in London on Monday.
The judge also delivered his ruling in the second of two trials, in which he made findings about the reliability of the Horizon computer system at the centre of the dispute.
He concluded that the system contained a number of “bugs, errors and defects” and that there was a “material risk” that shortfalls in Post Office branch accounts were caused by the system.
In a statement outside court after the hearing, James Hartley, partner at Freeths law firm which represented the claimants, said: “This judgment is vindication for the claimant group of postmasters - they have finally been proved to have been right all along when they have said that the Horizon system was a possible cause of shortfalls in their branch accounts.
“These claimants can now walk with their heads held high after all these years.
"This judgment, together with the settlement reached last week, are important stepping stones to achieving much-needed closure for these postmasters.
"They can now start to move on with their lives.”
Represented by a group of six lead claimants, the claimants alleged that the system contained a large number of software defects - which they say caused shortfalls in their accounts.
Some were made bankrupt, while others were prosecuted and even jailed for offences including false accounting, fraud and theft.
A spokesman for Freeths confirmed that “In 2017 there were 34 people from Lancashire who were part of the group action.”
There are also more than 34 criminal convictions of former subpostmasters, including Jacqueline McDonald, which are being reviewed by the Criminal Cases Review Commission (CCRC), which investigates possible miscarriages of justice.
Without admitting liability, the Post Office announced on Wednesday last week that it had agreed to settle the case with a £57.75 million payout.