I had never heard of the presumption that computer systems operate correctly until the Post Office Horizon scandal brought it to my attention. During my career I have worked as a developer, IT auditor, test manager, security manager and development team leader building complex financial systems with tough targets for accuracy. I therefore have no illusions about the difficulties of producing reliable software, and managing it so that it remains reliable.
With all this experience I knew the presumption was absurdly unrealistic and would inevitably lead to miscarriages of justice. Criminal cases and litigation typically involve unusual, even freakish events, rather than smooth, everyday routine. How can defendants or their legal teams, who are uninformed outsiders, possibly know what is happening within a complex software system and challenge the evidence?
While researching a 2020 article about the presumption and the Post Office scandal I read the Law Commission’s 1995 consultation paper and 1997 final report in which they recommended the repeal of section 69 of the Police and Criminal Evidence Act 1984 and the resulting presumption of computer reliability. I was surprised at the…
