A fundamental misunderstanding of the reliability of computers is partly to blame for the legal principle of being innocent until proven guilty being tarnished by the Post Office scandal, according to an academic research project.

One of the findings was that a lawyer defending a subpostmaster wrongly blamed for an account shortfall told the defendant that no jury would believe a prestigious government organisation would have a “dodgy computer”.

The Post Office scandal has already forced the government to consider changing the rules on computer evidence in court, now academics recommend the practice of reducing a defendant’s prison sentence as a reward for pleading guilty be reviewed.

Over 900 former subpostmasters were wrongly convicted of crimes based on evidence from the Post Office’s faulty computer system, Horizon. The government has accepted that the prosecutions were wrongful, and as part of their research, academics at the University of Exeter Law School have collected information from 35 people affected.

Their research report, Accessing injustice? Experiences of representation and the criminal justice system during the Post Office scandal, reveals that “the golden thread” of British justice, that people are innocent until proven guilty, “has been exposed by the Post Office scandal as more deeply tarnished than previously thought”.

The study was carried out by the experts at the Post Office research project and the Evidence Based Justice Lab at the University of Exeter Law School, Sally Day, Richard Moorhead, and Rebecca Helm, as well as Karen Nokes, from UCL.

Researchers said: “A birds-eye view of the criminal justice system provided to the researchers by former subpostmasters suggests ‘innocent until proven guilty’ was rarely taken seriously enough by any part of the criminal justice system that [they] came into contact with.”

As Computer Weekly has reported extensively, the Post Office scandal has already exposed the inadequacy of the legal rule on computer evidence that presumes a computer system has operated correctly unless there is explicit evidence to the contrary.

In May 2024, Parliament approved a law to overturn over 900 wrongful convictions that were based on Horizon system data, which was proved to be unreliable in the High Court in 2019.

The Department of Justice this year issued a call for information as it examines the role of computer evidence in the criminal justice system to prevent another Post Office scandal.

The researchers also report that the legal teams representing former subpostmasters that were being prosecuted didn’t always believe them when they claimed innocence because of a lack of understanding of computers and misplaced respect for the Post Office. One affected subpostmaster told them that their lawyer said: “No 12 people on a jury would believe that a prestigious government organisation would have a dodgy computer system.”  

It was this misinformed attitude and a lack of disclosure that, according to the research, “prompted several defence lawyers” to emphasise to clients that they were up against “a powerful, well-resourced institution”, and that “fighting the case was pointless”.

“Lawyers left to advise clients in the absence of disclosure from the Post Office typically encouraged their clients to plead guilty in the hope they would escape jail, sidestepping rather than addressing the client’s protestations of innocence,” said the researchers.

Moorhead, a professor at the University of Exeter, leads the research team. “Lawyers treated plea decisions as routine, when for the subpostmasters they were life-changing,” he said. “Protestations of innocence were not taken seriously. Their opponent behaved appallingly, but client stories were also not fully understood or investigated by those they had to put faith in.”

Moorhead said there was “profound carelessness in [defendant] treatment by their lawyers and the courts”.

Helm, also a professor at the university, said: “The pressures and cultures that allowed such injustice to occur are still operating in the criminal justice system today. Indeed, they may be worse.”

The researchers recommend that the Sentencing Council review its guidance on guilty pleas to ensure defendants are not pressured to plead guilty before disclosure is made, or where expert evidence is needed.

The Post Office scandal was first exposed by Computer Weekly in 2009, revealing the stories of seven subpostmasters and the problems they suffered due to the accounting software (see timeline of Computer Weekly articles about the scandal below).

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