Confirmation bias led Post Office to prosecute subpostmasters without investigation, inquiry told

Post Office investigators were so convinced that subpostmasters were cooking the books that they failed to investigate alleged IT problems, a public inquiry has been told.

Speaking to the statutory public inquiry into the Post Office Horizon scandal, Jeremy Folkes, former senior tech lead at the Post Office, said there was an understanding in investigation teams that there were concerns over the accounting system integrity, but they ignored them.

The former Horizon programme infrastructure assurance team leader said that the Post Office audit community, who were tied into the investigations community, had raised concerns about the number of accounting errors.

“Clearly, there was an understanding within the audit community that there were problems that were being pursued,” he said. “What I don’t understand is how magically this went from a system that was getting out with things being fixed, but maybe shaky, to everybody thinking it was in the right state to go around prosecuting without doing the correct investigation in the middle.”

More than 730 subpostmasters were prosecuted between 2000 and 2014 based on evidence from the controversial Horizon computer system used in branches. Over 80 former subpostmasters have so far had wrongful criminal convictions overturned, and more are expected. Many more were forced to pay the Post Office large sums of money to cover unexplained shortfalls, with businesses wrecked and lives ruined as a result.

Inquiry chair Wyn Williams said questions around the Post Office’s investigation and prosecution practices were key for the inquiry, and asked Folkes for his opinion.

Folkes said: “There were people in the investigations and prosecutions side in the Post Office who had confirmation bias. They were convinced that subpostmasters were misbehaving and if the system came up and showed that somebody was, say, £14,000 down, rather than taking into account whether the system was right, it gave them what they wanted. If you are an investigator or prosecutor, presumably your job is to investigate and prosecute.”

Folkes also questioned claims made by the Post Office that retrieving data from ICL/Fujitsu as evidence was expensive.

“Long before you prosecute, you presumably look at the system and the evidence supporting it,” he said. “There seems to be a view that they couldn’t get the data, but as we know, there was a process for data to be obtained centrally and in branches.”

Also questioned at the inquiry today (3 November) was retired IT expert Andrew Simpkins. He was brought into the Post Office as a French Thornton consultant as part of the programme management team to help oversee the trial, roll-out and release of Horizon.

Simpkins, who worked on the Horizon roll-out project from 1998 to the end of 1999, said that in his 35-year career, the Horizon programme was the most difficult he had ever worked on.

He confirmed that there were major concerns with the accounting integrity of Horizon and described his disbelief that subpostmasters could be prosecuted based on the accounting data.

“I never knew in my entire time on the project that there even was a Post Office investigations team, let alone that people could be prosecuted [based on Horizon data],” he said. “I had never been in a business environment where there is a discrepancy reported and someone goes to prison. This was beyond my conception.

“Where within the programme, at any time up to the roll-out, was that risk identified? It was in none of the documents and was never mentioned in a meeting. I know it sounds astonishing in retrospect, but I don’t think people in the team understood that if you have accounting discrepancies in branches that subpostmasters could not explain, that they would be responsible.”

Computer Weekly first reported on problems with the Horizon system in 2009, when it made public the stories of a group of subpostmasters (see timeline of articles below).