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By Paul Marshall and Stephen Mason.

On 10 March 2021, Mr Darren Jones MP, Chair of the Business Energy and Industrial Strategy Select Committee, (also chair of the Institute of Artificial Intelligence moved a Parliamentary debate that was responded to by Mr Matt Warman MP, Minister (Parliamentary Under-Secretary) for Digital, Culture, Media and Sport.

Moving the debate (formally, the legal status of automatic computer-based decisions) Mr Jones identified issues whose critical importance has been exposed by the scandal of the Post Office’s 15-year criminal prosecution of its postmasters on the basis of flawed evidence from its bug-ridden Horizon computer system. Appeals are now wending their way through the Court of Appeal at the instance of the Criminal Cases Review Commission, in some cases, almost 20 years’ after original trial and conviction.

Those prosecutions have generated what is arguably the largest miscarriage of justice in English legal history. As Mr Jones pointed out, this is a tragedy for the English legal system quite apart from the “untold human suffering” caused to those directly affected. Mr Jones described the state of English law as “dramatically out of date” and explained that the present legal presumption, that computers should be treated as operating reliably by analogy with machines (the position in English law since repeal of provisions under the Police and Criminal Evidence Act 1984 that until 1999 required a party relying on computer evidence to prove that the computer from which evidence was derived was working properly at the material time), as having “wide-ranging implications” and as “liable to cause significant harm and injustice” – as the Post Office scandal all-too clearly shows.

Among the important points made by Mr Jones were that “latent errors [in computer software] can occur frequently” and that “[a]chieving reliability in a computer system in the first place is difficult; it is even harder to assess and assure that reliability on an ongoing basis.” Recognition of these important facts is fundamental to ensuring that there is no repetition of the Post Office debacle. Mr Jones recorded that the Under-Secretary of State for Justice had referred the issue to the Lord Chief Justice in his capacity as chair of the Criminal Procedure Rule Committee – but considered that the issue went beyond that, and invited the Minister to use the powers of the government department responsible for digital and technology issues to refer the matter to the Law Commission. It was the Law Commission that was responsible for making recommendations to repeal legislation in 1999 – arguably with disastrous, and in any event insufficiently thought-through, consequences.

The Minister confirmed that Mr Jones’s request merited “very serious consideration”.

The importance of this short debate in placing this issue on the Parliamentary agenda is difficult to overstate. Computers and computer software permeate almost all aspects of our daily lives, but the latent propensity of software to fail is poorly understood and drawing a homespun analogy with the way in which mechanical instruments fail is apt to cause both confusion and injustice. It is high time that the issue received the legislative attention that it requires – not least to avoid likely tragic consequences of the issue remaining unaddressed.

The transcript of the debate is at

Stephen Mason  is a Barrister and an Associate Research Fellow at the Institute of Advanced Legal Studies. Paul Marshall is a Barrister at Cornerstone Chambers

Books and Journals

Stephen Mason and Daniel Seng, editors, Electronic Evidence and Electronic Signatures (5th edn, Institute of Advanced Legal Studies for the SAS Humanities Digital Library, School of Advanced Study, University of London, 2021)

Free Journal

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Digital Evidence and Electronic Signature Law Review (also available via the HeinOnline subscription service)