A “hugely significant” piece of evidence could posthumously exonerate a postmistress 27 years after she was convicted.
Long lost documents chronicling the “accident waiting to happen” Capture IT system which preceded Horizon were found dumped in a garage by a retired computer expert.
Adrian Montagu was lined up to be a key witness in the defence of Patricia Owen who used the software.
Since her conviction in 1998 her family have believed he failed to show up at court but Mr Montagu claims he was stood down for “no reason”.
Now he has lifted the lid on the “totally discredited” accounting software used to convict proud mrs Owen at Canterbury Crown Court.
Mr Montagu prepared a scathing report which described Capture as “an accident waiting to happen”, “totally discredited” and which produced “arithmetical or accounting errors”.
In a blistering assessment it says the software “is quite capable of producing absurd gibberish”, and describes “several insidious faults…which would not be necessarily apparent to the user”.
And in specific reference to Mrs Owen it concludes “reasonable doubt exists as to whether any criminal offence has taken place”.
The Capture accounting software was used in more than 2,000 branches between 1992 and 1999.
It was replaced by Horizon, the discredited Horizon accounting system, which is blamed for postmasters and postmistresses being framed for having their fingers in the till and convicted between 1999 and 2015.
The scandal was made famous by the ITV drama Mr Bates vs The Post Office starring Toby Jones as Sir Alan Bates who spent years doggedly exposing the appalling failures of the Post Office accounting scandal that cost lives, livelihoods, and reputations.
The first part of the final report for the Post Office Horizon IT scandal is due to be published next month.
Pat Owen was found guilty of theft from the Broad Oak Post Office in Sturry, near Canterbury, despite denying any involvement in a £6,000 shortfall in its accounts and given a suspended prison sentence.
Her family told how her life was ruined by the scandal and she was “shunned in the street”. The shame was a major factor in her ill health.
She narrowly avoided a prison sentence, but became a shell of her former self and rarely left home before her death from heart failure five years later, aged 62.
Her daughter Juliet said her mother fought with “everything she could”, adding: “To know that in the background there was Adrian with this (report) that would have changed everything, not just for mum but for every Capture victim after that, I think is shocking and really upsetting – really, really upsetting.”
The report was served on the Post Office lawyers who continued to prosecute sub-postmasters in the months and years after Mrs Owen’s trial.
The stunning discovery has shed new light on the scandal and helped c onvince Mrs Owen’s family that Mr Montagu did not abandon her d uring her hour of need.
He said: “I went to the court and I set up a computer with a big old screen.
“I remember being there, I remember the judge introducing everybody very properly…but the barrister in question for the defence, he went along and said ‘I am not going to need you so you don’t need to be here any more’.
“I wasn’t asked back.”
The report is now with the Criminal Cases Review Commission, which probes potential miscarriages of justice, and is currently examining 28 Capture cases.
Lawyer Neil Hudgell, representing more than 100 victims, said: “I’m as confident as I can be that this is a good day for Mrs Owen’s family.
“I think (the documents) could be very pivotal in delivering the exoneration that they very badly deserve.”
The Department for Business and Trade said: “Postmasters including Patricia Owen endured immeasurable suffering, and we continue to listen to those who have been sharing their stories on the Capture system.
“Government officials met with postmasters recently as part of our commitment to develop an effective and fair redress process for those affected by Capture, and we will continue to keep them updated.”