Nearly 1,000 people were wrongly convicted of crimes based on flawed evidence from a computer system used in Post Offices, and now that this is widely known to the public, the government has finally decided to review the legal rule that made the miscarriages possible.
Those who suffered the life-changing effects of being wrongly blamed for accounting shortfalls in Post Office branches they owned or worked in are rightly lauded for their fight for justice, and forcing a change to the rule on how computer evidence is used in court could be another part of their legacy.
The Post Office Horizon scandal has become widely known as one of the biggest miscarriages of justice in UK history. All the wrongful convictions shared one common denominator – evidence from Fujitsu’s flawed Horizon system was used in prosecutions, and the presumption in law that the computer was right unless proved otherwise meant innocent subpostmasters stood little chance of justice.
In 1999, the presumption was introduced into law on how courts should consider electronic evidence. The rule followed a Law Commission recommendation that courts should presume a computer system has operated correctly unless there is explicit evidence to the contrary. This replaced Section 69 of the PACE Act 1984, which stated that computer evidence should be subject to proof that it was operating properly.
While Post Office investigators fuelled the industrial scale miscarriages of justice, and Fujitsu kept silent about software problems, the legal presumption allowed them to happen.
In May 2022, the then government said it did not plan to review rules on the use of computer evidence in court, despite its link to the Post Office Horizon scandal. At the time, in response to a question, then Parliamentary under-secretary of state for justice, James Cartlidge, told Parliament: “We have no plans to review the presumption, as it has wide application and is rebuttable if there is evidence to the contrary.” He said that the Post Office Horizon scandal public inquiry would advise the government on the matter.
But since then, there has been a ITV drama about the scandal and a seismic backlash from the public, which has forced the government to finally address concerns over the presumption.
Too late, but welcome
For 15 years after the roll-out of Horizon, the Post Office – which has private investigation and prosecution powers with no need for police involvement – prosecuted subpostmasters for crimes such as theft and false accounting.
Hundreds of subpostmasters were sent to prison and many more received punishments such as being forced to do community service and having to wear electronic tags. They lived their lives with criminal records.
Hundreds were made bankrupt, losing their livelihood, and many struggled after being forced to pay the Post Office to cover shortfalls that didn’t exist outside the Horizon system. The lives of the victims and their families were severely affected, with several suicides linked to the scandal and many cases of illness caused by stress.
To prove their innocence, the people accused of the crimes were expected to be able to prove that the highly complex computer system they were mandated to use in their branches wasn’t working properly at the time the account shortfall they were being blamed for occurred.
Seema Misra, former subpostmaster in Byfleet, Surrey, was sent to prison while pregnant in 2010 after being wrongly prosecuted for theft.
During her trial Misra and her legal team said that the Horizon system was to blame for the shortfall, which senior Post Office lawyer Jarnail Singh described at the time as jumping on the “Horizon bashing bandwagon”. She had her conviction overturned in 2021.
Following the announcement of the government’s review of the law on computer evidence, Misra told Computer Weekly: “This is late, but definitely good news. You can’t just accept that the computer worked perfectly, which is what we always said.”
Jo Hamilton was a subpostmaster in South Warnborough, Hampshire, between 2003 and 2005. In October 2003, she started experiencing problems with mysterious losses and was unable to explain them. Faced with the prospect of a prison sentence, she pleaded guilty to false accounting to avoid it, despite having done nothing wrong.
“I don’t think it should be down to the accused to prove anything. I think it should be down to the prosecutor to prove that everything was working at the time,” she said. Hamilton welcomed the government review of the rules and lamented its late arrival. “The review has taken a while to get, but then I guess it took the Post Office scandal public inquiry and ITV drama to force it.”
Lee Castleton, who ran a branch in Bridlington, Yorkshire, was made bankrupt after challenging the Post Office in civil court action after it blamed him for unexplained accounting shortfalls.
His was a civil case where the PACE act doesn’t apply, but evidence from the Horizon system was used against him. He told Computer Weekly that the legal rule is grossly unfair. “To put the defendant onto the back foot in them having to prove a system, especially a huge system, didn’t work as it should, is unfair.
“A few years ago, some very eminent professors put together a reasons why it was imperative that the rule was changed and all those factors that they pointed out affected me in my case,” he added.
Former subpostmaster Scott Darlington, who had his wrongful conviction for false accounting overturned in 2021, had a shortfall of about £44,000 in his office, which he said at the time was caused by system errors.
Commenting on the government’s announced review of the legal presumption, Darlington told Computer Weekly. “I welcome the fact that it’s going to be looked at it, but it was clear there was problems with subpostmasters 10 years ago, they should have been making moves then to look at what they would do about the rules on computer evidence. Better late than never,” he added
Growing problem
Peer James Arbuthnot, who began campaigning for subpostmasters affected by Horizon problems over a decade ago when he was Jo Hamilton’s MP, said that he is pleased the government has called for evidence on “something that has been a growing problem for many years”.
“We all know, on the basis of our own experience of computers, that they are not always to be relied upon, and that they need regular updating because of that very unreliability,” he said. “For the courts to presume that computer evidence is reliable is therefore clearly absurd.”
He said the government was warned about the unfairness of the rules in 2019 by Justice Fraser, the managing judge in the High Court Group Litigation Order where subpostmasters proved the Horizon system was error prone: “Judge Fraser pointed out, in one of his Post Office judgments, that the presumption that computers were reliable needed to be reconsidered.”
“The Post Office had used that presumption as part of its weaponry to intimidate and browbeat the subpostmasters. Only if the subpostmasters could show that the computer might be wrong would they be allowed access to the evidence to show that it might be wrong. It was a shocking and ridiculous catch-22,” added Arbuthnot.
Arbuthnot pointed to the challenges replacing the legal presumption. “It will not be easy,” he stressed. “We do not want to require the prosecution in every case to prove that breathalysers work, or that email systems do what they are meant to do. That would clog up the already large backlog of court cases and cause huge expense to the public purse. So, we need to do something other than just get rid of the presumption.”
Working with experts and with fellow peer Beeban Kidron, Arbuthnot said that three possible solutions have been proposed to the government: “It is difficult, because we need to produce legislation which will be compatible with the rules of court for both civil and criminal cases, as well as being appropriate for computer technology.
“Computers are the most complicated things mankind has ever produced, and it is always a challenge for legislators to keep up with rapidly changing technology. I do hope, therefore, that the experts in these various fields will provide evidence on the issue and that the government will take it on board and react speedily.
“It is urgent – we must not see more scandals like the Post Office arising. Yet until the presumption is removed, that risk continues on a daily basis.”
Nonsense now and nonsense then
Experts are ready to contribute. Sam De Silva at the British Computer Society (BCS) said that the IT professional body will make a submission to the call for evidence. “As a principal, I think the review is probably long overdue. It’s something that obviously needs to be looked at,” he added.
He agreed that it is not a simple choice and that there must be a compromise: “I am not sure whether completely reversing the presumption is the most appropriate thing. I think a hybrid solution needs to be reached as we can’t go from one extreme to the other.” De Silva added that he hopes BCS members will be “feeding into this”.
Independent consultant and IT expert James Christie, who has extensive experience of software development, IT audit, testing and security management in the IT outsourcing industry, said: “About time too. It’s 25 years since the introduction of the absurd presumption of computer evidence’s reliability. It was nonsense in 2000, even more so now.”
The presumption, he said, “arose from lawyers’ and politicians’ failure to understand the nature of complex software systems”. In practice, he said the presumption reversed the burden of proof: “Defendants, like the Post Office’s victims, have to prove how they didn’t commit a crime.”
He added that the status quo benefits organisations that don’t build and manage software responsibly: “The presumption must be replaced by a requirement that suppliers of computer evidence can demonstrate they are in control of their systems.”
Computer scientist Steven Murdoch at University College London said that the presumption that computer evidence is reliable “frequently poses an obstacle to justice and a review is long overdue”.
He said that he hopes the outcome is a change in law that prevents anything like the Post Office scandal from happening again: “This will be a legacy that the victims of the scandal can be proud of.”
But he warned against focusing solely on the behaviour of the Post Office and Fujitsu and “particular circumstances” of the Horizon disputes: “The problems resulting from the presumption are more widespread and any solution will need to be capture the range of evidence that courts are expected to rely upon and the numerous ways that computers can fail.
“I also hope that proposed changes in law sets high expectations for the reliability of computer evidence when it could have life-changing implications,” he added. “The presumption has allowed companies to convince themselves and the courts that poor-quality computer systems are good enough. The public has a right to expect reliability when it matters and the IT industry must stand up to the challenge of building systems that meet the bar.”
The lawyers
Stephen Mason, who has campaigned for the presumption to be scrapped and co-edited Electronic evidence and electronic signatures, the open source practitioner text for judges and lawyers, stated: “It is welcome news that the Ministry of Justice is to re-examine the presumption. The Post Office Horizon IT scandal illustrated that it poses a substantial barrier to those who dispute evidence produced by a computer system or systems. The challenge is often insurmountable.”
Barrister Paul Marshall, with his junior Flora Page, offered their services free of charge to three former subpostmasters – Tracy Felstead, Janet Skinner and Seema Misra – who had their wrongful convictions overturned in the Court of Appeal in 2021.
He said that the Post Office scandal exposes the inability of the courts and the justice system to properly and effectively deal with electronic evidence. “The scandal is, at base, a legal scandal. For 20 years, the courts were hoodwinked by an institution that, with its lawyers, was willing to unscrupulously exploit that weakness. The Post Office did so ruthlessly and conspicuously successfully.
“The Post Office had known about faults, errors and defects in its Horizon computer system since its roll-out in 1999, but had concealed them, in part by a pitiless strategy of prosecuting and bringing civil proceedings against its subpostmasters to protect its immediate commercial interests that were threatened by known data integrity issues.
“The fundamental task of the court is to evaluate evidence. It is profoundly troubling that in a pervasive dimension of modern life – digital technology – the courts have shown themselves unable to perform their basic function effectively and reliably.
“The Post Office now faces a sea of claims for malicious prosecution for miscarriages of justice on a scale without precedent in English legal history.”