Lords want to repeal law that backs reliability of computer evidence in wake of Post Office scandal

Former sub postmasters celebrate outside the Royal Courts of Justice in London after being cleared of theft and false accounting because of the Post Office’s defective Horizon accounting system – TOLGA AKMEN/AFP via GETTY IMAGES

The House of Lords is attempting to change a law that presumes computer evidence is reliable to prevent a repeat of the Post Office Horizon scandal.

A cross-party group of peers including veteran post office campaigner Lord Arbuthnot have tabled an amendment that would revoke the current assumption that information provided by computers is always accurate.

The Post Office lobbied for the rule in the 1990s before the scandal in which hundreds of sub-postmasters were convicted of theft, based on evidence from the Horizon computer system used in their branches.

This evidence was later proved to be unsafe owing to errors in the Fujitsu software that created account shortfalls, for which sub-postmasters were blamed and some jailed. Nearly 100 people have so far had their convictions overturned and the Government is considering exonerating hundreds more.

The current legal rule stipulates that courts should presume a computer system has operated correctly unless there is explicit evidence to the contrary.

Verify

It replaced a law which said that prosecutors using evidence derived from computers had to verify that the system it came from was working correctly. It was introduced in 1999 by the then Labour government following a Law Commission recommendation.

Documents that the Post Office submitted to the Law Commission in 1995 show that it viewed these “technical requirements” as a barrier to successful prosecutions.

Lord Arbuthnot speaks to the media outside the Department for Business and Trade in central London before a meeting of the independent Horizon Compensation Advisory Board – James Manning/PA

The amendment, tabled by Lord Arbuthnot, online harms campaigner Baroness Kidron, LibDem peer Lord Clement Jones and Labour’s Baroness Jones, would place the onus on the prosecution to show that the evidence from the computer was reliable and that the machine had been operating properly at all times.

Lord Arbuthnot told The Telegraph: “It is extraordinary that a presumption that computer evidence is correct has survived the Horizon scandal. I believe that presumption needs to be changed as a matter of urgency.”

He accepted that it was “not absolutely clear” what it should be changed to but he said he was probing the Government to come up with an alternative rather than necessarily forcing the amendment to a vote.

Baroness Kidron said: “In the story of the sub postmasters, we saw corporate entities outsourcing the bugs of a technological system onto the least powerful – in this case the sub postmasters – and it felt horribly familiar.

Assumption

“The Mr Bates amendment I have laid, reverses the assumption in UK law that computers are reliable. All computer systems have bugs – that is normal – what is crazy is to pretend otherwise.”

A report commissioned by the Ministry of Justice (MoJ) recommended that a prosecutor, like the Post Office, which deploys electronic evidence, should automatically provide sufficient details of their systems to demonstrate that they were professionally managed.

However, in May 2022, the then justice minister James Cartlidge disclosed that the Government had no plans to review the presumption as it had a wide application and was “rebuttable” if there was evidence to the contrary.

The MoJ declined to comment on Friday pending the outcome of the public inquiry which is expected to consider the arguments over whether the law should be changed to end the assumption that computers are always accurate.

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