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

Ever since 2019, when Sir Alan Bates and his fellow Justice for Subpostmasters Alliance members exposed the Post Office’s misuse of the rule to prosecute subpostmasters, there have been calls for change.

The debate featured peers James Arbuthnot and Kevan Jones, who introduced the amendment, which sets out to remove the presumption. The pair are long-time campaigners for justice for subpostmasters affected by the scandal.

During the debate, an amendment to remove the presumption that computers are reliable was moved by peer Shami Chakrabarti.

The presumption was introduced in 1999, in section 69 of the Police and Criminal Evidence Act 1984. It enabled the Post Office to prosecute subpostmasters using unreliable evidence and even no evidence.

As Chakrabarti put it during the debate: “Under the old Section 69, a party seeking to rely on computer evidence had to show that there was no improper use of the computer, that it was operating properly at all material times and that any faults did not affect output.

“It allowed for court rules to scrutinise computer evidence. Since the repeal of that vital protection, a common-law presumption of computer reliability and accuracy has applied, in effect reversing the criminal burden of proof in some cases and leading to serious harm, most recently in the Post Office Horizon scandal. Several Justice Ministers have acknowledged this since 2018.”

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

The 1999 change was, at the time, supported by the Post Office, which had described the prosecution having to prove the computer was working as “somewhat onerous from a prosecution viewpoint”.

What followed saw hundreds of people wrongfully convicted of crimes because they were to blame for unexplained account shortfalls in the Post Office branches, that were actually caused by errors on the Post Office Horizon system. Many were sent to prison.

The government, panicked by ITV’s dramatisation of the Post Office scandal making it headline news, introduced legislation to overturn these convictions en masse in 2024.

Arbuthnot told fellow peers that “evidence derived from a computer is hearsay. There are very good reasons why we treat hearsay evidence with caution. To admit hearsay evidence is a step in itself, but to presume that it is reliable is a giant stride beyond that.”

But what came a day later, also in the House of Lords, felt like the government supported change, although a government minister’s ambiguity means uncertainty remains.

Asked by peer Sal Brinton whether he and other ministers work together to ensure that “this change happens as soon as possible”, fellow peer and minister Jason Stockwood said: “I can confirm to the noble Baroness that the department will work to try to ensure that comes to its logical conclusion.”

While ambiguous, IT professionals are united that the “logical conclusion” would be the removal of the presumption of courts that computer evidence is reliable.

Brinton said: “Everyone in [previous debate], including the minister, agreed that this must be changed, not least following the Horizon scandal.”

Computer Weekly contacted the government for more clarity about Stockwood’s comment. A Ministry of Justice spokesperson said: “We remain committed to creating a justice system that works better for everyone, which is why last year we launched a call for evidence to examine the use of computer-generated evidence within criminal proceedings. We are carefully considering responses and will respond in due course.”

The department’s call for evidence came over a year ago, in January 2025, when the government called on experts to guide it on what needs to change.

At the beginning of the amendment debate on 11 February, Chakrabarti said: “I hope my noble friend the Minister will tell us what has come as a result [of the call for evidence], because that is too long, I suggest.”

During the debate, peer Jones said: “I am not opposed to consultation, but I am sorry, this government is hiding behind consultation. Once the consultation is finished, we then need action, but that is not happening, not just in this area, but in a whole host of other areas.

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 Horizon accounting software, which led to the most widespread miscarriage of justice in British history (see below timeline of Computer Weekly articles about the scandal since 2009).

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