Fri, May 17, 2024

Findings of the Expert Team in Bates & Others v Post Office Limited (Horizon Issues Trial)

Many people will have seen the British Post Office scandal dominating the news in recent months, highlighting the numerous subpostmasters who have been wrongly accused, and even convicted of, financial misconduct. After an ITV drama (which aired in the new year) brought the case to wider public attention, the media train has been non-stop. Those who are avid followers of the case may even be aware of the YouTube channel dedicated to publicizing the public inquiry that is underway.

There are many facets to the Post Office case and this article covers the involvement of Kroll professionals who investigated the financial accounting system deployed in the UK’s Post Office branch network, known as “Horizon.” In a group action brought by Alan Bates & Others versus Post Office Limited, the “Horizon Issues” trial (which concluded in 2019), was a landmark legal case that investigated the reliability of the Horizon system. The expert witness team instructed on behalf of Alan Bates & Others was led by Siobhan Forster, Kroll Senior Director in the Technical Disputes team within the Data Insights and Forensics practice. The oral testimony at trial was provided by Jason Coyne, a Senior Consultant at Kroll.

The Expert Role

Instructed by James Hartley of Freeths LLP, the expert team were tasked with identifying how robust Horizon was (as a financial accounting system). Other instructions (listed here in summary) included whether subpostmaster accounts could be accessed remotely (remote access) and what controls and measures were in place to ensure the reliability of the Horizon accounting processes and procedures (and whether such were available contemporaneously to subpostmasters).

Analysis and Findings

The analysis included review of hundreds of thousands of documents provided in disclosure. The team's extensive review of the system design documents, error logs, audit reports and software release notes (amongst other documentation) resulted in vital evidential findings drafted in the form of two lengthy expert reports and several joint expert reports prior to trial. Using sophisticated case management tools, the expert team was able to draw links between defect logs that identified multi-party knowledge of bugs, errors and defects. The team was therefore able to submit further requests for information (RFIs), seeking further disclosure from the Post Office to evidence the extent of the flaws within the system.

Remote Access

In a technical estate as large as the Post Office's network (and with the technical landscape that was deployed at that time), remote access capability would not be unexpected. Most IT experts would expect there to be capabilities to manage the branch estate remotely, in order to maintain it, and would likely opine as such. The important considerations to this are how remote access was deployed, managed and conducted and why. As IT experts, our team was able to provide the upfront opinion that remote access would be expected; however, such procedures should operate with strict controls and policies to ensure system integrity is maintained. This knowledge enabled the team to identify the relevant evidence in relation to remote access issues and whether such policies were in place and/or strictly adhered to as per best practice. This guidance enabled more targeted disclosure review.

Bugs, Errors and Defects

The findings of the expert reports evidenced that the Horizon system had an abundance of bugs, errors and defects which led to accounting errors, many resulting in financial shortfalls. Whilst some of the bugs, errors and defects were acknowledged by the Post Office, many were not. Thanks to the sophisticated search techniques deployed by our team, we were able to construct a timeline of defect existence highlighting that, for the most part of Horizon's operation, there had been significant bugs, errors and defects with the abilities to cause shortfalls in branch accounts.

The expert reports also highlighted how flawed processes restricted the ability to adequately investigate the issues raised by subpostmasters and evidenced a failure to adequately rectify misaligned accounts.


Overall, the findings of the Horizon Issues trial exposed systemic failures within the Post Office. In the post-trial judgement, handed down by Justice Fraser, it was found that instead of acknowledging and addressing subpostmaster concerns appropriately (despite the discrepancies arising as a result of the Horizon system itself or the failure of process and/or rectification), the Post Office pursued discrepancy payments, fines, charges and prosecutions, based on flawed evidence. As a result of the Horizon Issues trial, many subpostmasters have had their convictions overturned. The expert evidence findings assisted the court in ultimately determining that the convictions were unsafe and have prompted calls for reform to prevent similar injustices from occurring in the future. Alan Bates and the subpostmasters campaign daily to seek reform and adequate compensation.

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