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IT scandal exposes legal rule that made it easy for Post Office to prosecute the innocent
Lawyers call for changes to digital evidence rule that made it easier for the Post Office to ‘bamboozle courts’ and make subpostmasters pay a heavy price for its IT failings
Two separate events in 1999 have become inextricably linked in the process of destroying the lives of hundreds of subpostmasters across the UK.
Although unrelated, together they were to have a devastating impact on law-abiding people, criminalising them due to a faulty IT system and a legal rule that denied them a fair trial.
In 1999, the government-owned Post Office began installing a new core accounting and retail system, known as Horizon, in thousands of Post Office branches across the country. The system, from Fujitsu, was seen as a revolution at the time, automating manual tasks such as bookkeeping.
At about the same time, a presumption was introduced into law on how courts should consider electronic evidence. The new rule introduced in 1999 followed a Law Commission recommendation for courts to presume that a computer system has operated correctly unless there is explicit evidence to the contrary. This legal presumption replaced a section of the Police and Criminal Evidence Act (PACE) 1984, which stated that computer evidence should be subject to proof that it was in fact operating properly.
The new rule made it easier for the Post Office, through its private prosecution powers, to convict subpostmasters for financial crimes when there were accounting shortfalls, based on data from the Horizon system. One barrister has said that, as a result, the courts were “bamboozled” by the Post Office. Innocent subpostmasters who were convicted paid a heavy price.
It wasn’t long after the introduction of Horizon that subpostmasters began to report unexplained accounting shortfalls. These business people, who own and run Post Office branches, were deemed responsible for the losses if they could not prove otherwise.
Because the 1999 legal rule meant that data from the Horizon system was presumed accurate, losses were therefore considered the fault of the subpostmaster, whether through theft or incompetence. Subpostmasters were forced to use their own cash to cover shortfalls or, in many cases, were prosecuted for theft and false accounting if they couldn’t afford, or refused, to make up the unexplained shortfalls.
The Post Office did not have to prove in court that the computer system was not at fault. Some subpostmasters served prison sentences, hundreds lost their livelihoods and there is at least one suicide linked to the scandal.
Over a 15-year period, more than 900 subpostmasters were prosecuted for financial crimes based on Horizon data. Many claimed that this data was wrong – and they were proved right years later in the High Court.
Although many subpostmasters suspected that the computer system was to blame, proving it would require expert IT or forensic accounting skills. In 2004, on the advice of a friend, former subpostmaster Alan Bates contacted Computer Weekly about the problems. In 2009, after contact was made by another former subpostmaster, Lee Castleton, Computer Weekly revealed the stories of seven subpostmasters who had suffered at the hands of Horizon (see timeline of Computer Weekly articles below).
But this was just the tip of the iceberg and Bates went on to lead more than 500 subpostmasters to victory in a multimillion-pound litigation in the High Court, which began in late 2018. The case proved that the Horizon system had bugs that could cause accounting shortfalls. In fact, High Court judge Peter Fraser described the Post Office’s stance that Horizon could not be the cause as “amounting to the 21st century equivalent of maintaining that the Earth is flat”.
Yet the legal rules meant the Post Office could prosecute without providing evidence that the computer system was not at fault.
Post Office knew Horizon had errors
It has since emerged that, during those prosecutions, the Post Office knew that Horizon had errors that could cause accounting shortfalls.
“The Horizon case proved that judges should agree to the disclosure of more technical evidence relating to errors and bugs,” said Stephen Mason, editor of the practitioner text for judges and lawyers, Electronic Evidence. “For some reason that I cannot understand, judges often refuse defence requests for relevant evidence. This happened in the case of Seema Misra. If the judges in Seema Misra’s case had ordered appropriate disclosure by the Post Office, the members of the jury might have reached a different conclusion about her guilt.”
Former subpostmistress Seema Misra was sent to prison while pregnant after being found guilty of theft in 2010. Her conviction was referred to the Court of Appeal by the Criminal Cases Review Commission (CCRC) and will be heard in March.
Unlike the government-owned Post Office, subpostmasters did not have the money to pay for lawyers or forensic accountants that could help them discover and prove the cause of accounting shortfalls.
Those that did get expert support had different experiences. For example, speaking to Computer Weekly in 2015, Andrew Clark, visiting professor in information security at Royal Holloway University of London, said that in 2005 he was called as a witness for the defence in a case brought by the Post Office against a subpostmaster accused of false accounting.
The digital forensics expert, who was hired by solicitors in relation to the case, told Computer Weekly that after he raised questions about the integrity of the Horizon system, the Post Office dropped the case.
The Horizon scandal is widely seen as the biggest miscarriage of justice in modern English history. It has also revealed, in stark terms, the inadequacy of the legal presumption that computers are always right.
Paul Marshall, barrister at Cornerstone Barristers, said: “If the Post Office had been required to prove affirmatively that its Horizon system was working properly at the material time and it had given proper disclosure of Horizon error records, then it would not have been able to succeed in its prosecutions and its subpostmasters, with perhaps some small exceptions, would not have been convicted.”
In March last year, a few months after Judge Fraser’s ruling in the Bates and others versus Post Office case in the High Court in December 2019, the CCRC sent a total of 47 cases of potential miscarriages of justice to the Court of Appeal for review. This was the biggest group referral in history. Six former subpostmasters have already had their names cleared in Southwark Crown Court and the rest will appeal their convictions in the Court of Appeal in March.
And there could be many more. The CCRC said it has about 25 cases of subpostmaster prosecutions currently under review, while the Scottish CCRC recently took what it described as an “unusual step” of writing to 73 people with criminal convictions potentially linked to the Post Office’s Horizon errors. If the SCCRC concludes potential miscarriages of justice, it will refer them to the Scottish High Court, where appeals are heard.
But even this could just be scratching the surface of a wider problem of computer-generated miscarriages of justice. The 900-plus subpostmaster prosecutions based on Horizon data could potentially be just one group example. Computer systems are used in every corner of the economy and society and it is not infeasible that thousands of people have been prosecuted based on computer evidence that was wrong.
Marshall said there was nothing to suggest the Post Office was unique in its ability to succeed in civil claims and criminal prosecutions on the basis of flawed computer evidence. “The weaknesses that the Post Office ruthlessly exploited to its own advantage were systemic, both as a matter of substantive law and of procedure (disclosure),” he said. “ It follows that it is very likely that there will be many others who have been convicted of offences or held liable in civil claims on the basis of unreliable computer evidence.”
Opportunity to change the rules
There is now an opportunity to change the rules, supported by a very powerful and public case study, and the government has at least revealed that it is listening. Last August, Marshall was invited by Alex Chalk MP, minister at the Ministry of Justice (MoJ), to submit a paper to the MoJ on suggestions for improving the existing approach to the proof in court proceedings of computer-derived evidence. The paper was submitted to the MoJ in November and is now published.
The paper recommends that when electronic evidence is used in legal proceedings, the party relying on the electronic evidence should automatically provide sufficient details of their systems to demonstrate that they are professionally managed.
Chalk has referred the paper and its recommendations to the Criminal Procedure Rule Committee chair and Computer Weekly understands that has triggered a process of consideration that will take months.
“Both the Civil Procedure Rule Committee and the Criminal Procedure Rule Committee must review the rules on the disclosure of computer evidence,” said Marshall. “The reason for this is that the existing rules on disclosure simply do not work, as the Post Office scandal painfully reveals.”
Marshall said the Horizon scandal was a major embarrassment both for the government and for the courts. “It is simply embarrassing for the judiciary, at all levels, that the courts have been bamboozled by the Post Office and its lawyers over such a long period,” he said. “Given the increasing pervasiveness of digital technology, there seems to be a pressing case for judicial education.”
Stephen Mason, a barrister no longer in practice and one of the authors of the paper, has been researching and recommending change on the use of electronic evidence in court since 2004. He told Computer Weekly: “I have been trying to persuade the legal profession for over a decade to take the subject seriously. One can only hope that the Post Office Horizon scandal will change things.”
Mason said the scandal illustrates the importance of not taking the “reliability” of computer evidence on trust. “The purpose of a trial is to test the evidence, but clearly the evidence of the Horizon computer system was never properly tested until 2019,” he added.
“It is to be sincerely hoped that justice will now take centre place when dealing with evidence from computer systems and devices of all types.”
Timeline of the Post Office Horizon articles since Computer Weekly first reported on it in 2009
- May 2009: Bankruptcy, prosecution and disrupted livelihoods – postmasters tell their story.
- September 2009: Postmasters form action group after accounts shortfall.
- November 2009: Post Office theft case deferred over IT questions.
- February 2011: Post Office faces legal action over alleged accounting system failures.
- October 2011: 85 subpostmasters seek legal support in claims against Post Office computer system.
- June 2012: Post Office launches external review of system at centre of legal disputes.
- January 2013: Post Office admits Horizon system needs more investigation.
- January 2013: Post Office announces amnesty for Horizon evidence.
- January 2013: Post Office wants to get to bottom of IT system allegations.
- June 2013: Investigation into Post Office accounting system to drill down on strongest cases.
- July 2013: Post Office Horizon system investigation reveals concerns.
- October 2013: End in sight for subpostmaster claims against Post Office’s Horizon accounting system.
- October 2013: Former Lord Justice of Appeal Hooper joins Post Office Horizon investigation.
- November 2013: 150 subpostmasters file claims over “faulty” Horizon accounting system.
- September 2014: Fresh questions raised over Post Office IT system’s role in fraud cases.
- December 2014: MPs blast Post Office over IT system investigation and remove backing.
- December 2014: Why MPs lost faith in the Post Office’s IT investigation, but vowed to fight on.
- December 2014: MPs to debate subpostmaster IT injustice claims.
- December 2014: MP accuses Post Office of acting “duplicitously” in IT investigation.
- January 2015: MPs force inquiry into Post Office subpostmaster mediation scheme.
- January 2015: Post Office faces grilling by MPs over Horizon accounting system.
- February 2015: Post Office CIO will talk to any subpostmaster about IT problems, promises CEO.
- March 2015: Post Office ends working group for IT system investigation day before potentially damaging report.
- March 2015: MPs seek reassurance over Post Office mediation scheme.
- March 2015: Retiring MP aims to uncover truth of alleged Post Office computer system problems.
- April 2015: Post Office failed to investigate account shortfalls before legal action, report claims.
- April 2015: Criminal Courts Review Commission set to review subpostmasters’ claims of wrongful prosecution.
- May 2015: IT system related to subpostmaster prosecutions under review by CCRC.
- June 2015: Post Office looking to replace controversial Horizon system with IBM, says MP.
- July 2015: Campaigners call for independent inquiry into Post Office Horizon IT system dispute.
- October 2015: James Arbuthnot takes Post Office IT fight to House of Lords.
- November 2015: The union that represents Post Office subpostmasters has warned of a problem with the Horizon accounting system.
- November 2015: An email from Post Office IT support reveals a problem with the Horizon system and supporting processes that could lead to accounting errors.
- November 2015: Group litigation against Post Office being prepared in Horizon dispute.
- February 2016: Post Office faces group litigation over Horizon IT as subpostmasters fund class action.
- June 2016: Post Office chairman Tim Parker says there would be “considerable risk” associated with changing its Horizon computer system.
- November 2016: The legal team hired by a group of subpostmasters will take their case to the next stage.
- January 2017: The group action against the Post Office that alleges subpostmasters have been wrongly punished for accounting errors gets a green light from the High Court of Justice.
- March 2017: 1,000 subpostmasters apply to join IT-related group litigation against Post Office.
- April 2017: Investigation into claims of miscarriages of justice in relation to a Post Office accounting system has appointed a forensic accountant firm.
- May 2017: Hundreds of subpostmasters have applied to join IT-related legal action since March.
- July 2017: Post Office defence in computer system legal case due this week.
- August 2017: Campaigners submit initial evidence in group litigation against Post Office over controversial Horizon IT system.
- October 2017: Subpostmasters’ group action against the Post Office reaches an important milestone.
- November 2017: An end is in sight for subpostmasters’ campaign against alleged wrongful prosecution, which they blame on a faulty computer system.
- November 2017: The High Court judge managing the subpostmasters versus Post Office legal case over an allegedly faulty computer system tells legal teams to cooperate.
- January 2018: Forensic investigation into Post Office IT system at centre of legal case nears completion.
- April 2018: Criminal Cases Review Commission forensic examination of the IT system at the centre of a legal case against the Post Office has raised further questions.
- May 2018: Post Office branches unable to connect to Horizon computer system for several hours after morning opening time.
- October 2018: After over a decade of controversy, next week marks the beginning of a court battle between subpostmasters and the Post Office.
- November 2018: Case against Post Office in relation to allegedly faulty computer system begins in High Court.
- November 2018: High Court case in which subpostmasters are suing the Post Office has revealed a known problem with a computer system at the core of the dispute.
- November 2018: A High Court trial, where subpostmasters are suing the Post Office for damages caused by an allegedly faulty IT system, ends second week.
- November 2018: Post Office director admits to Horizon errors and not sharing details with subpostmaster network.
- November 2018: The High Court trial in which subpostmasters are suing the Post Office has reached an important stage.
- December 2018: CCRC may hold off subpostmaster decision until after Post Office Horizon trial.
- December 2018: Court case where subpostmasters are suing the Post Office set to span at least four trials and extend into 2020.
- January 2019: Subpostmasters’ campaign group attacks Post Office CEO Paula Vennells’ New Year honour amid ongoing court case.
- January 2019: Thousands of known errors on controversial Post Office computer system to be revealed.
- March 2019: Tech under spotlight at High Court in second subpostmasters versus Post Office trial.
- March 2019: Post Office considered Horizon IT system “high-risk”, court told.
- March 2019: CCRC watching Post Office Horizon trial closely.
- March 2019: Judge rules that Post Office showed “oppressive behaviour” in response to claimants accused of accounting errors they blamed on Horizon IT system.
- March 2019: Post Office “lacked humanity” in the treatment of subpostmasters, says peer.
- March 2019: A High Court judge heard that the Post Office did not investigate a computer system error that could cause losses, despite being offered evidence.
- March 2019: The Post Office legal team in the case brought by more than 500 subpostmasters has called for the judge to be recused after questioning his impartiality.
- March 2019: A senior civil servant asked the Post Office to repay public money it had wrongly allocated to paying legal costs.
- April 2019: Subpostmaster claimants’ legal team makes application for the Post Office to pay millions of pounds of costs associated with trial.
- April 2019: Post Office to appeal judgment from first Horizon trial.
- April 2019: The Post Office’s claim that the judge overseeing the case concerning its controversial Horizon IT system was biased has been dismissed.
- April 2019: MP questions government over Post Office Horizon case.
- April 2019: Government says no conflict of interest in trial despite Post Office chairman’s dual role.
- May 2019: The Court of Appeal has refused the Post Office’s application to appeal a major decision in the Horizon IT trial.
- May 2019: The Post Office has applied for permission to appeal judgments from the first trial in its IT-related legal battle with subpostmasters.
- May 2019: The judge in the Post Office Horizon trial has ordered the organisation to pay the legal costs of its courtroom adversaries, and refused to give permission to appeal a major judgment.
- June 2019: Post Office asks Court of Appeal for permission to appeal judgment in first Horizon trial.
- July 2019: The Post Office has admitted that some subpostmasters are at risk of accounts not balancing due to an error it does not understand.
- July 2019: Problem revealed during High Court trial left subpostmaster with £18,000 surplus after IT system failed to register full amount of cash scanned in.
- August 2019: Subpostmasters suffering slow running and frozen terminals while Post Office searches for a fix to issues apparently caused by a software update.
- August 2019: The Post Office has fixed the latest problems with its Horizon system, affecting hundreds of branches.
- October 2019: A High Court judgment for a trial that focused on the Post Office’s IT system at the centre of a multimillion-pound litigation will be announced early next month.
- November 2019: The Court of Appeal has rejected a Post Office application to appeal judgments made in its multimillion-pound battle with subpostmasters over IT system failures.
- November 2019: Peer calls for clear-out of Post Office board after Court of Appeal confirms major court defeat.
- December 2019: The Post Office has settled its long-running legal dispute with subpostmasters, and will pay £57.75m in damages.
- December 2019: Subpostmasters ended their legal battle with the Post Office at the optimal time, according to the lawyer that managed the High Court action.
- December 2019: Subpostmasters proved right on IT system failures as calls for full public inquiry mount.
- December 2019: Criminal Courts Review Commission to review Horizon judgment “swiftly”.
- December 2019: National Federation of Subpostmasters cries foul after court ruling on controversial computer system.
- December 2019: Former Post Office CEO apologises to subpostmasters over Horizon scandal.
- December 2019: Call for former Post Office CEO to step down from public roles after IT court battle lost.
- January 2020: Fujitsu must face scrutiny following Post Office Horizon trial judgment.
- January 2020: Subpostmaster group calls for government to pay legal costs for Horizon trial.
- January 2020: Why subpostmasters are calling on the government to pay Horizon trial costs.
- January 2020: Department for Business, Energy & Industrial Strategy says it did not make decisions in the Post Office’s recent court battle.
- January 2020: Government should not be allowed to dismiss subpostmasters’ claims over Horizon IT scandal.
- January 2020: Police sent information about potential Fujitsu staff perjury in subpostmaster prosecutions.
- January 2020: Prosecutions are a significant step closer to being sent to the Court of Appeal as Criminal Courts Review Commission forms a group of commissioners to review them.
- January 2020: Alan Bates: The “details man” the Post Office paid the price for ignoring.
- February 2020: The government has refused to pay the huge legal costs subpostmasters incurred in their battle with the government-owned Post Office, which they won.
- February 2020: Members of Parliament seeking a public inquiry into the Post Office Horizon scandal face huge challenges, but pressure and time could force justice.
- February 2020: Calls for inquiry into Post Office IT scandal increase in Parliament, with cross-party support.
- February 2020: Care Quality Commission to review concerns over Paula Vennells’ appointment after they were raised by a former NHS consultant psychiatrist.
- February 2020: Government admits it was too passive managing Post Office as parliamentary pressure builds.
- February 2020: Minister says Post Office IT experts misled the government when it asked questions about subpostmasters’ concerns over Horizon IT system.
- March 2020: Boris Johnson commits to “getting to the bottom of” Post Office Horizon IT scandal.
- March 2020: Boris Johnson’s commitment to inquiry into Post Office scandal in doubt.
- March 2020: MPs call on PM to commit to full public inquiry into Post Office Horizon IT scandal.
- March 2020: Those who did not play by the rules in Post Office Horizon scandal “should face prosecution”.
- March 2020: MPs told to hold to account those responsible for Post Office Horizon IT scandal.
- March 2020: The Post Office has sparked anger with secret settlements with subpostmasters outside the recent legal action against it.
- March 2020: Labour MP Karl Turner tells Computer Weekly that the Post Office Horizon scandal is the most grotesque version of predatory capitalism he has ever seen.
- March 2020: MP Kevan Jones has warned a government minister not to repeat the mistakes of predecessors in relation to the Post Office Horizon IT scandal.
- March 2020: Criminal Cases Review Commission to use Microsoft Teams to ensure review of subpostmaster prosecutions is held on time.
- March 2020: Post Office postpones subpostmaster compensation scheme amid Covid-19 crisis.
- March 2020: Meeting reviewing subpostmaster applications to appeal criminal prosecutions moves into second day.
- March 2020: Subpostmaster prosecutions to be considered by Court of Appeal for miscarriages of justice.
- March 2020: How subpostmasters made legal history with biggest referral of potential miscarriages of justice.
- April 2020: Met Police examines information about evidence given in court by Fujitsu staff on the Horizon IT system.
- May 2020: Subpostmasters who had their lives ruined by the Post Office’s faulty IT system have received their damages after a High Court victory.
- May 2020: A senior Post Office executive at the centre of an IT scandal, who tried to mislead a High Court judge in relation to it, has left the organisation without fanfare despite many years of service.
- May 2020: Post Office re-examines hundreds of prosecutions that could have resulted from faults in Horizon IT system.
- June 2020: A campaign group representing subpostmasters wrongly prosecuted for theft and false accounting by the Post Office is raising money to help clear the names of victims of the scandal.
- June 2020: Subpostmasters to force scrutiny of government’s role in Post Office IT scandal.
- June 2020: The Criminal Cases Review Commission sends 47 more subpostmaster cases to Court of Appeal and asks government to review private prosecution powers.
- June 2020: Select committee chair writes to former Post Office CEO demanding answers over her role in IT scandal.
- June 2020: The government has been accused of launching a review that fails in getting to the bottom of one of the biggest miscarriages of justice in UK history.
- June 2020: Subpostmasters will not cooperate with government review into IT scandal.
- June 2020: The government’s proposed review of the Post Office IT scandal has received a further setback as forensic accountants join subpostmasters in refusing to back it.
- June 2020: Call for government review of Post Office Horizon scandal to have the power to force individuals to give evidence under oath.
- June 2020: Subpostmasters seeking justice in the Post Office Horizon IT scandal are regaining momentum in Parliament.
- June 2020: Healthcare regulator will be discussing concerns about former NHS boss chairing an NHS trust at an upcoming meeting.
- June 2020: Second Sight is working with law firm in appeals by subpostmasters against criminal convictions in Horizon IT scandal.
- June 2020: Post Office and Fujitsu blame each other for many of the failings in the Horizon IT scandal that wrecked lives.
- June 2020: Parliamentary Justice Committee to hold short inquiry into the rules and regulations surrounding private organisations’ ability to initiate criminal proceedings.
- July 2020: Victims of the Post Office Horizon IT scandal need to raise thousands of pounds in a week or those responsible for their suffering will avoid scrutiny.
- July 2020: The government is set to face scrutiny over its involvement in the Post Office Horizon IT scandal, described as one of the biggest miscarriages of justice in modern UK history.
- September 2020: The government repeats that it won’t pay victims’ legal costs and confirms review into the scandal will not have the power to call witnesses.
- September 2020: Subpostmasters still not being told about all the known errors in the controversial Post Office branch accounting and retail system that they use.
- October 2020: The Post Office has chosen not to contest 44 out of 47 appeals, meaning most are likely to have their names cleared, but others still face a Court of Appeal battle for justice.
- October 2020: MPs are demanding the government holds a full statutory public inquiry into the Post Office IT scandal.
- October 2020: NHS regulator continues enquiries about the appointment of former Post Office CEO at Imperial College Healthcare NHS Trust as more damning details emerge.
- October 2020: Government minister met with former subpostmaster online in an attempt to get victims of the Post Office Horizon scandal involved in government review.
- October 2020: The Post Office is focusing urgently on fixing an IT error suffered by a subpostmaster amid the ongoing IT scandal.
- October 2020: Labour politicians are calling for the government to give the Post Office Horizon scandal inquiry the power to force witnesses to give evidence if they don’t cooperate.
- October 2020: Imperial College Healthcare NHS Trust has asked for external review of its process when appointing controversial executive.
- November 2020: Government faces scrutiny of its handling of the Post Office IT scandal that destroyed subpostmasters’ lives and livelihoods.
- November 2020: Post Office branches offline during busy business hours after suffering an IT error that the Post Office said related to IT from supplier Fujitsu.
- November 2020: Fujitsu is refusing to explain what caused a national system outage in Post Office branches last week, despite the Post Office confirming the issue was the fault of the supplier.
- November 2020: The Metropolitan Police opens criminal investigation into Fujitsu staff who gave evidence in trials of subpostmasters wrongly prosecuted and even imprisoned for financial crimes.
- November 2020: Post Office criticised over vagueness of its explanation of the cause of a UK-wide IT failure that saw subpostmasters unable to do business.
- November 2020: Post Office says planned firmware update caused the problem that left branches unable to do business for 90 minutes.
- November 2020: Court documents reveal the names of the Fujitsu employees under investigation for potentially providing misleading information in criminal trials.
- November 2020: The government allowed the Post Office to “run amok” and destroy lives, says complaint to Parliamentary Ombudsman.
- November 2020: Campaigning politician demands access to documents that could prove that the Post Office lied.
- December 2020: Government denies responsibility for the abuse inflicted on subpostmasters by the Post Office over faulty IT system.
- December 2020: CEO at the centre of the scandal that saw innocent people bankrupted and some sent to prison steps down from NHS role as pressure for her resignation grows
- December 2020: History made as subpostmasters wrongly prosecuted in Horizon IT scandal have convictions quashed.
- December 2020: The appointment of a former Post Office executive, who tried to mislead a judge, in the Football Association of Wales has been questioned by an MP.
- December 2020: Court of Appeal indicates subpostmasters can pursue appeal route that could do more damage to Post Office’s reputation.
- January 2021: NHS trust defends its director appointment process following an external review of its recruitment of former Post Office CEO Paula Vennells.