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Computer and law experts respond to call for opinions on computer evidence

IT and legal experts have made submissions to a government consultation on the use of computer evidence in court

Karl Flinders
By
Published: 15 Apr 2025 0:15

Legal and IT experts have made submissions to the government’s call for views on the current rules around the use of computer evidence in court, which closes today.

The wider public understanding of the Post Office Horizon scandal, which saw innocent subpostmasters jailed based on flawed evidence from an accounting system, forced the government to look again at a controversial law which presumes computers work correctly.

The scandal saw hundreds of subpostmasters blamed, prosecuted and convicted of crimes after losses appeared on the accounting system used in branches. The figures produced by the Horizon system, which is supplied by Fujitsu and used in thousands of branches, was presumed to be accurate in court.

But a 2018 High Court case proved that Horizon errors caused phantom losses that subpostmasters were blamed and punished for. Hundreds of people who were prosecuted based on the flawed evidence have had their convictions overturned.

In January, the Ministry of Justice issued a 12-week call for evidence as it examines the role of computer evidence in the criminal justice system to prevent another Post Office scandal. The deadline for evidence closes today (15 April).

In 1999, a 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 Police and Criminal Evidence (PACE) Act 1984, which previously stated that computer evidence should be subject to proof that it was operating properly.

Read more about the rules on computer evidence

Although there have been calls for many years for reform from the likes of former lawyer Stephen Mason, it was the Post Office Horizon scandal which finally persuaded the government to act.

Mason, who is submitting his recommendations, said: “What I have called for is the setting up of either a judicial rules body or a group of people to write a code of practice for judges and lawyers.”

He said this would be something like the rules of court or judicial rules which he says need to be “updated regularly by people that know what they are talking about”.

IT profession and lawyers have their say

In its submission to the call for evidence, BCS, The Chartered Institute for IT, said: “The presumption that computer-generated evidence is inherently reliable is increasingly unfit for purpose in modern criminal prosecutions.” It said the Post Office Horizon scandal illustrates this.

“At present, rebutting the presumption of computer evidence is exceptionally difficult,” added the BCS. “It has been shown that defendants in cases like Horizon have struggled to access crucial system logs, error reports, and documentation that could undermine the assumed reliability of the evidence. Additionally, some of the lower courts often lack the specialised technical expertise required to scrutinise complex software and digital data, meaning that challenges to the reliability of computer evidence must overcome both procedural and substantive hurdles that favour the status quo.”

The Law Society said due to the increased complexity of technology the law should not assume that computers are flawless. In its submission to the government’s call for evidence it said existing laws must keep pace with technological advances or public confidence in the justice system could be damaged.

Richard Atkinson, president of the Law Society said: “Given the increasing complexity of technology, we should not assume computers are flawless.

“To ensure that the use of computer evidence does not lead to miscarriages of justice, there should be assurance, regular review and disclosure of the system’s technical standards and performance across the board. Although this call for evidence relates only to criminal proceedings, the government should consider applying similar safeguards to computer evidence used in civil cases too.”

He added: “While innovation can bridge existing gaps of unmet legal needs, it is important that use of technology in the justice system is fair, transparent and reliable. Any proposals put forward should prioritise justice as a vital public service affecting every single member of society.”

Computer Weekly first exposed the scandal in 2009, revealing the stories of seven subpostmasters and the problems they suffered due to the Post Office Horizon accounting software - the most widespread miscarriage of justice in British history.

Read expert analysis of computer evidence rules

Read more on IT legislation and regulation