Ian Ritchie / The Herald Business HQ / March 2024
"THE LAW IS AN ASS, an idiot” said Mr Bumble in Oliver Twist, and that was absolutely true during the enormous number of unfair convictions suffered by sub-postmasters during the Horizon Scandal.
But this is a tech column, so I need to be more specific; what was particularly idiotic was the way that the courts were not allowed to challenge computer evidence in courts.
Today, everybody knows about the Horizon scandal but for many years it was only the trade magazine Computer Weekly and the satirical Private Eye that reported it, plus a few BBC radio documentaries. That all changed in January 2024 when ITV screened their drama Mr Bates vs the Post Office and blew the story wide open, making it impossible to ignore, even by the government, which for years had been trying to look the other way.
The specific idiocy was way computer behaviour was treated.
Back in 1999 a presumption was introduced on how courts should consider electronic evidence. The new rule followed a Law Commission recommendation for courts to presume that a computer system has operated correctly unless there is explicit evidence to the contrary.
This legal presumption replaced a section of the Police and Criminal Evidence Act (PACE) 1984.
As it happens, I was President of the British Computer Society at that time, the UK’s professional body for computing. I don’t recall us being consulted about this change, but we were relaxed, assuming that any known errors in systems would be disclosed by their suppliers, as is required by courts.
Also in 1999, the Post Office began installing their Horizon system to modernise the financial management of their sub-post offices. Horizon, developed by Fujitsu, automated tasks such as bookkeeping and accounting. But it wasn’t long before the Horizon system began to report unexplained accounting shortfalls, and the Post Office’s reaction to this situation was to aggressively prosecute their sub-postmasters to recover the “losses” which had been reported.
For most computer professionals, the first conclusion would have been that the system is likely to have significant errors which should be investigated.
But because the new legal rule meant that the behaviour of the Horizon system must be presumed to be accurate, losses were automatically considered to be the fault of the sub-postmaster, through theft or incompetence.
Defence attorneys were effectively forbidden to challenge the behaviour of the system, which was, by legal presumption, working perfectly.
It turned out to be impossible for those who were accused, without access to knowledge of the many errors – which were well known inside the Post Office and Fujitsu - to demonstrate that Horizon was prone to error, and over 700 sub-postmasters, most of whom had been previously regarded as trustworthy in their local communities, became convicted criminals.
To computer experts, the thought that a computer system had to be automatically regarded as behaving perfectly and couldn’t have errors in it is laughable. Computer systems are designed and built by software engineers, and software engineers are, like everybody else, quite fallible.
We can see this demonstrated almost every day when bank, airline or ticketing systems fail for a while when faults are identified and resolved.
This aggressive persecution of sub-postmasters was exacerbated by the fact that the Post Office, as a former government agency, was allowed to pursue their own prosecutions and didn’t have to involve the independent Crown Prosecution Service.
This allowed them to allegedly suppress all evidence of system faults, and wrongly deny that Fujitsu could amend individual branch details without the sub-postmaster’s knowledge. It's claimed they refused to reveal the suspiciously high number of sub-postmasters prosecuted. The police are investigating these failures to disclose.
In the case of Lee Castleton, who conducted his own defence, a request for the numbers of sub-postmasters complaining about Horizon errors was claimed to be too costly, at £3,000, to provide. The Post Office then went on to incur £300,000 in legal fees to prosecute Castleton and when he lost, he became liable for those legal costs, forcing him into bankruptcy.
In 2022, as this scandal was beginning to become more widely understood, Labour MP Kevan Jones asked James Cartlidge, then Parliamentary Under-Secretary of State for Justice whether he had plans to assess the legal presumption of reliability of computer evidence. His response was that there were no such plans.
Finally, in January this year, Justice minister Sarah Sackman KC launched a 12-week consultation by the Ministry of Justice on this issue, saying: “We must learn the lessons of the Post Office scandal. A blanket “no questions asked” acceptance of the accuracy of digital evidence can have a devastating impact on people’s lives”.
It will be interesting to see the results of this consultation - maybe, as a result, the law might become a bit less of an ass.
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