At least eight convictions predating the Horizon Post Office scandal are being looked at by the body investigating potential miscarriages of justice, Sky News has learned.
The Criminal Cases Review Commission (CCRC) has confirmed it is examining multiple cases of former sub-postmasters affected by Capture software.
The computer accounting system was used in the early 1990s, prior to Horizon being introduced to Post Office branches from 1999 onwards.
Horizon was at the centre of the Post Office scandal and saw hundreds of sub-postmasters wrongly convicted of stealing from their branches.
The Kroll report, commissioned by the government earlier this year, found that Capture had bugs and glitches and there was a reasonable likelihood it had caused cash shortfalls too.
Lord Beamish, the former Labour MP Kevan Jones, has been supporting victims and is calling for the government to extend current legislation to automatically quash convictions.
The Post Office (Horizon System) Offences Act was passed in May but does not include Capture victims.
Lord Beamish told Sky News he has raised the issue with the justice secretary and called for a House of Lords debate.
"The government are going to have to take this seriously," he said. "We can't have a situation where we have a two-tier system where people get exonerated from Horizon and the Capture cases are either forgotten or have to go through a very lengthy legal process to get their names cleared."
He added he had "little faith" in the CCRC's "ability to deal with cases", after multiple Horizon cases were referred to the body years ago.
"The problem with these cases is the lack of evidence… that has been destroyed or lost - so actually proving some of these cases through that process will be very difficult.
"Therefore I think a blanket exoneration like we had with Horizon I think has got to be discussed and considered for these cases."
The CCRC told Sky News it has five cases under review "in which the Capture IT system could be a factor".
It also said it is "seeking further information" on eight cases referenced in the Kroll report.
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The CCRC added that the time taken for a case review to be completed was dependent on the "complexity" of each case "and how readily available information about it is". In a statement, it admitted: "The availability of information can be a particular hurdle in older cases."
Chris Roberts's mother, Liz Roberts, was convicted in 1999 of stealing £46,000 from the Post Office and spent 13 months behind bars.
Liz, who was in the advanced stages of Alzheimer's disease, passed away earlier this year.
Chris said she was jailed four days before he turned 17, and he used to have "nightmares" that she was "going to die in there".
"There was no evidence of any financial gain because they went through everything. And obviously the money wasn't in our accounts because it didn't exist," he added.
Despite being offered "three deals" by the Post Office to plead guilty, Liz refused and was sent to prison.
Chris believes that the 2019 High Court win by Horizon victims was a missed opportunity for the Post Office to look back at Capture cases.
"It would have been worth something then because my mum would have died knowing that everybody else knew she was innocent," he said.
"My dad would have died knowing that the love of his life wasn't vilified as a criminal."
Chris wants his mother exonerated and "those actively responsible" to "stand up in court… and justify themselves".
A Department for Business and Trade spokesperson said: "We were horrified to learn about the issues with the Capture system and are working closely across government to thoroughly examine Kroll's independent report and consider what action should be taken.
"We continue to listen to postmasters and others who have been sharing their views on the report's findings since its publication last month."
(c) Sky News 2024: Post Office scandal: At least eight convictions linked to Capture software being investigated
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