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Post Office prosecutions during Horizon go-live phase are ‘frightening’

The Post Office used subpostmasters as guinea pigs to test its software and take the rap for its errors

Karl Flinders
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Published: 06 Mar 2024 8:30

The Post Office’s decision to prosecute subpostmasters using Horizon evidence during the software’s early roll-out phase was “frightening”, according to an IT expert who exposed its deficiencies.

With the Post Office accused of perverting the course of justice in its prosecutions of subpostmasters, forensic IT expert Jason Coyne described how the subpostmasters were treated as “guinea pigs”.

Coyne did an early investigation into Horizon, as part of a court case in 2003, which revealed bugs in the Horizon system. He also acted as an expert witness for the 555 subpostmasters, led by Alan Bates, who proved the software was flawed in a 2018/19 court case. 

When Horizon was being rolled out in thousands of Post Office branches in the early 2000s, the Post Office knew, as with all software, there would be bugs, he said. “We know the Horizon system went live with a number of issues – and there is nothing unusual about that. Every system goes live with bugs, but there has to be a judgement about their severity.”

Coyne said bugs are often measured on severity and organisations make a judgement on the number of bugs they can accept going live based on these severity measures. “This is accepted by people and Horizon clearly went live in that state. The subpostmasters were used as guinea pigs to test that system,” he said.

But when rolling out software with known bugs, Coyne said it is essential that every single potential software and user problem is thoroughly investigated. That didn’t happen with Horizon. “The fact that the Post Office used that early roll-out period to prosecute people was frightening because lots of people in the Post Office will have known [Horizon was] going live with lots of bugs,” he said.

In 2003, Coyne was appointed as an expert witness by a court during a legal battle between the Post Office and Julie Wolstenholme, the former subpostmaster at a branch in Cleveleys, Lancashire. In 2001, the Post Office attempted to sue Wolstenholme for the return of equipment used in the branch after her contract was terminated. But in a counterclaim, she said her employment was terminated unlawfully and raised questions about the reliability of the Horizon computer system used in branches.

Coyne found that helpdesk calls made by Wolstenholme showed evidence of software errors. “We were getting narrative within those call logs, from 2001, talking about problems such as data corruption, as well as hardware and power failure. We could see information from that early period that showed the type of problems were not caused by the subpostmaster,” he said.

Read how, in preparation for the 2018 High Court battle, forensic IT expert Jason Coyne
outsmarted an ‘aggressive’ Post Office to get to truth after inspection ‘madness’

In his report, Coyne said: “There seems to be a number of [helpdesk call] logs which talk of ‘large discrepancies’ in stock figures, trial balances with ‘all sorts of figures showing minus figures’. From a computer system installation perspective, it is my opinion that the technology installed at the Cleveleys sub-post office was clearly defective in elements of its hardware, software or interfaces. The majority of the errors noted in the fault logs could not be attributed to being of [the subpostmaster’s] making or operation of the system.”

The Post Office attempted to convince Coyne to change his report, but when he refused, to hush up the report, it paid Wolstenholme a settlement, which included her having to sign a non-disclosure agreement (NDA). The Post Office kept Coyne’s report quiet.

Edward Henry KC, acting for victims of the Horizon scandal, wrote in his closing statement for phase four of the statutory public inquiry that Post Office staff conspired to pervert the course of justice when they “suppressed” and “withheld” evidence. 

Henry referred to the Cleveleys case in his closing statement. He wrote: “Already the Post Office was more concerned with reputational fallout if word should get out that Horizon accounting data was unreliable, rather than recognising that Cleveleys was a red flag, requiring them to investigate whether Horizon accounting data was in fact reliable.”

Computer Weekly first exposed the scandal in 2009, revealing the stories of seven subpostmasters and the problems they suffered as a result of the Horizon system (see below timeline of all Computer Weekly articles about the scandal).

• Also read: What you need to know about the Horizon scandal •

• Also watch: ITV’s Post Office scandal documentary – Mr Bates vs The Post Office: The real story •

Read all Computer Weekly articles about the scandal since 2009

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