Computers and the truth: a cross-disciplinary analysis of the statutory reliability requirement

Similarly to the United Nations Commission on International Trade Law’s (UNCITRAL) Model Law on Electronic Commerce, since the enactment of the Electronic Trade Documents Act 2023, UK law imposes an ex ante reliability requirement on computer systems that fall within the Act’s scope. Prior to this, under English law, the reliability of computer systems fell to be assessed ex post, in that computer evidence needed to be reliable in order to be admissible in court. This article argues that while, as demonstrated by the Horizon litigation, the assessment of reliability for the purposes of the law of evidence involves asking similar questions to those underpinning a reliability assessment for the purposes of UNCITRAL’s legal instruments, the reliability requirement in the law of evidence is of limited use in incentivizing the development and adoption of reliable computer systems in commerce because it comes into play (i) only after the computer system has already been deployed and a dispute has arisen (that is ‘ex post’) and (ii) since the 1990s, only if the presumption that computer evidence is reliable can be rebutted at trial by the party contesting reliability. The article draws on literature on the reliability standard found in UNCITRAL instruments, on computer engineering literature, and on the Horizon litigation to explain what reliability means, arguing that while the assessment may be similar, unlike ex post assessment, a requirement to assess ex ante incentivizes system providers to ensure a high degree of reliability from the start.