Use of computer evidence in court to be interrogated

Currently, there is a presumption that computers work correctly and any evidence generated by software is accurate, unless there is evidence to the contrary.

However, the limitations of this were highlighted by the wrongful convictions of hundreds of innocent sub-postmasters in the Post Office Horizon scandal. Faults in the Post Office’s accounting software system proved the fallibility of digital evidence and the potential for devastating miscarriages of justice if evidence is not thoroughly interrogated. 

The 12-week call for evidence launched today (Tuesday 21 January) will invite views from across the justice system and beyond on the presumption.

By seeking new ways to ensure people are better protected from miscarriages of justice, this expert review will help to build on the government’s broader efforts restore public confidence in policing and in the criminal justice system through our Plan for Change.

Justice Minister Sarah Sackman KC said

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.

We need to carefully consider how we can both use and interrogate digital evidence in court. Ensuring people are protected from miscarriages of justice is vital, and one part of the government’s Plan for Change.

Computer evidence forms a substantial part of many modern prosecutions, particularly in crimes such as fraud, which can involve thousands of digital documents. Digital evidence is also often used in rape and serious sexual offence cases.

Any change requiring the prosecution to prove any computer device works ‘correctly’ could impact how quickly cases can be completed. Therefore, any reform must be well thought out and future proofed.

The call for evidence is seeking expert input on how computer evidence should be defined, and what could fall into scope of any change to the law. For example, distinctions might need to be drawn between general digital evidence like text messages or social media posts, and evidence which has been specifically generated by a computer system or software.

It will seek views from organisations and individuals with experience of the criminal justice system, along with those with expertise in computers and software.

The miscarriages of justice which occurred in the Post Office cases were down to deliberate failures to properly interrogate and disclose evidence – which prevented postmasters and others from effectively challenging the reliability of the Horizon computer system evidence. 

Any changes to the presumption would not be able to further protect against instances where parties mislead a court on the accuracy of the evidence. But lying in court – or perjury – is a separate crime already.

However, removing or changing this presumption could mean defendants are better equipped to interrogate computer evidence against them, and would put more onus on the party supplying the digital evidence to ensure it can stand up to scrutiny.

Further Information

• Find the Call for Evidence here
• In 2000, section 69 of the Police and Criminal Evidence Act 1984, which covered the use of evidence from computers, was repealed. Prior to this, it was necessary to prove that a computer was operating properly and was not used improperly before any statement in a document produced by the computer could be admitted in evidence. The position since 2000 has been a common law rebuttable presumption that a computer was operating correctly at the material time, unless there is explicit evidence to the contrary
• There has been a call for changes to this presumption from a number of those with expertise in both software and the criminal law, and the recent Horizon scandal, amongst other cases, has highlighted the urgent need to review this position
• Since the repeal of s.69 of the scope and scale of ‘computer evidence’ in criminal prosecutions has proliferated, in ways which may not have been fully foreseen at the time. It is important that we consider what legislative changes might be needed to the way in which this type of evidence is dealt with in prosecutions. However, any proposed changes must be well thought through and informed by a wide range of expertise and best available evidence to mitigate against any unforeseen consequences which could delay or derail the prosecution of suspected offenders, or indeed lead to further miscarriages of justice