Joanne O'Donnell died seven years ago aged 64 after she was given a seven-month jail sentence following a trial at Manchester Crown Court in 2007.

The Criminal Cases Review Commission (CCRC) referred her case to the Court of Appeal after being contacted by Mrs O'Donnell's husband Ian in the wake of the Horizon IT scandal.

Errors made by Horizon software, which was made by tech firm Fujitsu and used by the Post Office, led to the wrongful convictions of dozens of people for false accounting and theft between 1999 and 2015.

Some 700 people were convicted in the 16-year period. Out of that number, 132 cases have been through the appeals process resulting in 83 overturned convictions and 49 unsuccessful appeals, according to the Post Office.

But three judges dismissed Mr O'Donnell's appeal on Tuesday.

Lord Justice Holroyde said appeal judges had previously considered appeals against conviction by many former Post Office staff prosecuted many years ago after being convicted of dishonesty offences.

He said those cases raised issues about abuse of process and the safety of convictions, "having regard to concerns about the reliability" of Horizon.

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The judge said Mrs O'Donnell had denied wrongdoing but was convicted by a jury after a five-day trial.

He added: "For the reasons we have given, this is not one of the exceptional and rare cases in which it would be appropriate to conclude that Mrs O'Donnell's conviction is unsafe on either of the abuse of process grounds which have been advanced on her behalf."

'We are satisfied the conviction is safe'

In a written ruling, Lord Justice Holroyde said: "We have read a moving letter by Mr O'Donnell, which makes clear the distress which Mrs O'Donnell and her family suffered as a result of her conviction.

"We can well understand why he remains convinced of her innocence and wishes to clear her name.

"We must, however, decide this appeal in accordance with the law rather than on a basis of sympathy."

The judge added: "We are satisfied that the conviction is safe. This appeal therefore fails and must accordingly be dismissed."

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Lawyers had raised a number of concerns about the safety of Mrs O'Donnell's conviction.

They included a "material failure of disclosure", "the unreliability of Horizon data that was essential to the prosecution", and the "poor level of investigation".

Lawyers representing the Post Office opposed the appeal.