Data is never pure. Errors creep in. It’s annoying when bad data dents your credit rating; when it tells the police you’re likely to be a criminal, it could ruin your life.
Criminal convictions have been obtained because courts were told that data was infallible when in fact it was full of mistakes. Indeed, the most important single miscarriage of justice in the UK’s criminal systems in the past quarter of a century began when the Horizon accounting system falsely reported discrepancies and non-existent shortfalls in Post Office branch accounts.
Because Horizon was believed over branch managers,, 736 sub-postmasters and mistresses were prosecuted for fraud between 2000 and 2014. In December 2019, the Post Office settled with 555 claimants for a total of £58m, with the court finding that the Horizon system suffered from around 30 main “bugs, errors and defects”. In spring 2021, the Court of Appeal overturned 72 of the convictions. For some, it was too late: by early 2022, 33 of those wrongly prosecuted were dead, four of them reportedly at their own hands.
