IT experts call for review of ‘computer is always right’

A professional body for IT specialists has added its voice to calls for a review in the legal presumption that evidence from a computer is correct unless proven otherwise. Amid the continuing public furore about the Post Office Horizon scandal, BCS, the Chartered Institute for IT, today said the law must be reviewed to avoid future miscarriages of justice. 

Since 1999, courts have been required to follow the common law assumption that a computer producing the evidential record is working properly and that the record is admissible. Previously, section 69 of the Police and Criminal Evidence Act 1984 required anyone introducing computer-generated evience to show the system was operating correctly and not being used improperly. The change followed the Law Commission’s 1997 review of the law on hearsay evidence.

Dr Sam De Silva, partner at international firm CMS and chair of the BCS’ Law Specialist Group, said that the Post Office scandal shows the dangers of courts unquestioningly accepting the output of IT systems as reliable evidence.

'There remains a legal presumption that the computer is always right,' De Silva said. 'The Post Office could rely on the common law position that the courts were entitled to assume that the IT system was operating correctly.' This put the burden on accused sub-postmasters to prove that the outputs and logs from the Horizon computer system were not accurate,’ he said. 'Yet how could non-IT specialists be expected to prove this when even some experienced IT professionals would find it a challenge to do so?’

If the Post Office had been required to prove that Horizon was operating reliably, most of the individual cases against postmasters might have had a different outcome, he said. In future: 'Organisations relying on evidence generated from computer systems to support prosecutions should be required to prove that the underlying computer system is reliable; we hope this will be a clear recommendation from the current [public] inquiry.'

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