Academics study impact of computer evidence presumption on lawyer perceptions

An academic study will test the hypothesis that lawyers’ and judges’ perceptions of the reliability of computer-based evidence contributed to the miscarriage of justice seen in the Post Office IT scandal.

The Hearsay from a computer study will look beyond the “particulars of the rules of the use of computer evidence” and consider the impact the presumption that computer evidence is accurate has had on the legal profession over the 27 years it has existed.

The legal rule, which presumes a computer was working properly at the time of an alleged crime, has been cited as one of the major causes of the scandal, which is one of the biggest miscarriages of justice in history, having led to some 1,000 subpostmasters being wrongly convicted of crimes due to shortfalls on the error-prone Horizon IT system they used for accounting. Many were jailed.

Read: Post Office Horizon scandal explained: Everything you need to know

Kate Leader, senior lecturer in criminal law at Queen Mary University of London, and Jessica Shurson, assistant professor of law at the University of Sussex, are leading the project.

We hypothesise that lawyers’ and judges’ perceptions of the reliability of computer-generated evidence contributed to the miscarriages of justice seen in the Post Office cases due to an overreliance on the reliability of computer-derived evidence

Leader said: “Alongside revisiting the particulars of the rules of evidence on computer-generated evidence, it is imperative to consider the impact that 25 years of this flawed presumption has had on the perceptions of legal practitioners as to the reliability of computer-generated evidence.

“We hypothesise that lawyers’ and judges’ perceptions of the reliability of computer-generated evidence contributed to the miscarriages of justice seen in the Post Office cases due to an overreliance on the reliability of computer-derived evidence that has developed over a quarter century of practice under this evidential presumption.”

Paul Marshall, a barrister who represented former subpostmasters at the Court of Appeal, said: “This is a most welcome project. The presumption has left its mark on the legal profession. It’s just laziness and ignorance, and it’s profoundly embarrassing for the legal profession.

Read more: Court rule that fuelled Post Office’s prosecution rampage: Everything you need to know

“The past 25 years, since the Law Commission made its recommendations, have been the consequence of extraordinary naivety and wishful thinking on the part of many lawyers.”

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.

There is currently a government review of the rules on the use of computer evidence in court, spurred by the fallout of the Post Office scandal. The Department of Justice issued a call for evidence in January 2025.

Furthermore, an amendment to the controversial rule that courts presume computers are reliable was formerly proposed during a House of Lords debate on 11 February this year.

Peer James Arbuthnot, long-time campaigner for justice for subpostmasters, is a leading voice in efforts to change the flawed rules on computer evidence.

He recently told Computer Weekly that changes to rules on digital evidence are heading in the right direction.

He said former minister and peer Alison Levitt had agreed to take the issue away and see what could be done. “We had two meetings, the most recent being on 15 July, and I was sure that she was determined to sort it out. Sadly, she did not survive the reshuffle, but I do believe she has started the process on the right trajectory, and I also believe she is likely to do her best from the backbenches to ensure that the rule changes do what we agreed was necessary.

“This is a complicated process which is a work in progress, but I believe it is probably headed in the right direction,” he added.

A Ministry of Justice spokesperson said: “The call for evidence received views from a wide range of stakeholders. We continue to engage across government to carefully consider this issue.”