Operating Correctly Unless There Is Evidence to the Contrary: The UK Ministry of Justice on Evidence Generated by Software, January 2025

On January 21, 2025, the UK Ministry of Justice opened a call for evidence on the use of evidence generated by software in criminal proceedings. It was set to end on April 15, 2025, and it says that "A paper summarising the responses to this call for evidence will be published in due course." Its aim, it says, is "to increase our evidence base and understanding of the ways in which evidence produced by software is handled in criminal proceedings." Parts of it follow, not the whole.

The Presumption

The paper's foreword says the current principles were established "over two decades ago, with the common law presumption that a computer was operating correctly unless there is evidence to the contrary." Then it puts it more simply: "In simple terms, 'the computer is always right', unless someone can show it is not."

Before 2000, the paper explains, the admissibility of computer evidence was subject to section 69 of the Police and Criminal Evidence Act 1984. That section required it to be shown, among other things, "that at all material times the computer was operating properly, or if not, that any respect in which it was not operating properly or was out of operation was not such as to affect the production of the document or the accuracy of its contents". In 1997 the Law Commission recommended that section 69 be repealed without replacement. In 2000, the paper says, "it was replaced with a common law (rebuttable) presumption that the computer was operating correctly at the material time."

The paper explains what rebuttable means here: "if it can be shown that the software may not have been functioning correctly, the burden shifts to whoever is seeking to rely on the evidence to prove that it was."

What the Foreword and Introduction Say

The foreword says the limits of the presumption "have been highlighted starkly by" a scandal "which saw hundreds of sub-postmasters wrongly convicted." Those convictions, it says, "were based on evidence which we now know to have been false, due to faults in the" accounting software system it names, "clearly demonstrating the fallibility of evidence produced by software."

Computer evidence, the paper says, "now proliferates in many prosecutions, particularly in crimes such as fraud, rape and serious sexual offence cases," and is "widely used in cases which see high volumes of prosecutions such as driving offences." So, it says, "it is important when examining this area we consider any ramifications for the effective functioning of the criminal justice system."

What Would Be In and Out of Scope

The ministry wants any change "carefully defined to only include that evidence which is generated by software, including Artificial Intelligence and algorithms." Its examples of what it would bring into scope, which it calls "non-exhaustive," include accounting programs, "automated fraud or plagiarism detection software" and "automated reporting based on records entered into devices, such as handheld devices for entering patient interactions in a hospital."

Evidence "merely captured or recorded by a device," the ministry believes, should be excluded: for example messages between people and emails, digital photographs and video, "Breathalyser readouts" and "Mobile phone extraction reports." It asks for views on whether "these are the right boundaries".

Some of the Questions It Asked

Its questions begin with the presumption itself: whether it is "fit for purpose in modern criminal prosecutions," how easy or difficult it is "at present for this presumption to be effectively rebutted," and what barriers stand in the way. It asks for examples from other jurisdictions or situations "where the reliability of software must be certified." And if the law were changed and a solution relied on expert witnesses, it asks "what expertise and qualifications would that person require? To your knowledge are there sufficient such people at present?"

For a fault that raises no error, the question about barriers is the hard one. A doubter has to point at something, and a system that fails silently leaves little to point at.