In the final day of the committee stage of progressing the Data Bill through the House of Lords before the Christmas break, we attempted to persuade the government of the urgent need to consider how computer evidence is treated in legal proceedings.Currently, UK law contains a presumption that computers are working correctly when they produce material that is used in court. This can be rebutted, but only by evidence that is unlikely to be available without access to the computer system, putting the burden of proof squarely on the shoulders of those least able to provide it.It may seem somewhat surprising that this issue has not been resolved long ago, particularly given the stark reminder we had last year in relation to the Post Office Horizon scandal. But, as it has not yet been addressed, colleagues and I are taking the opportunity of the Data Bill to press the government on this problematic legal practice.I raised the issue at second reading asking, What is the governments position when it comes to the reversal of the burden of proof in computer evidence?... It should certainly be the case that that evidence is put to proof.As the barrister Paul Marshall, who acted for many of the subpostmistresses and masters affected by the scandal, has pointed out, computer evidence is hearsay, with all the limitations that implies.As a start point, we only need our own, everyday experience of using computers to understand the obvious reality that modern computer programs are not fully tested or by any means bug free when they are put onto the market.In many ways it is their sheer scale that renders them too large to be exhaustively tested. If we accept this, there is no other logic than to assert that, as a consequence, they are far from infallible and should be treated by the courts as such.And yet, since 1999, courts have applied a common law presumption, in both criminal and civil proceedings, of the proper functioning of machines - that is to say, the information from the computer can be presumed to be reliable. Marshall explained that in the Post Office case it put the onus on the defendants to explain to the jury the problems they encountered with the Horizon system when all they could actually do was point to the shortfalls they had experienced. The uncritical admission of computer evidence in the Post Office Horizon case was in itself an injustice As my colleague Baroness Kidron pointed out, the reality is that anyone who knows the first thing about programming or computer science knows there are bugs in the system. Indeed, any one of us who has agreed to an update for an app or computer software understands that bug fixing is a common aspect of program maintenance.Perhaps the most convincing thing of all is looking at software contracts. For the past 20 years at least, a contract is likely to contain words to this effect: No warranty is provided that the operation of the software will be uninterrupted or error free, or that all software errors will be corrected.It is more than five years since Mr Justice Fraser, now Lord Justice Fraser, made it clear in his High Court ruling that the uncritical admission of computer evidence in the Horizon case was in itself an injustice. The burden to say in what way the computer was unreliable fell on the party without access to the system, while the party with access namely, the Post Office via its subcontractor Fujitsu - had no similar responsibility to reveal what might be unreliable.It is critical to make the point that in no sense should it be determined by the Data Bill or indeed any statute, that computer evidence should be accepted or given weight by the court - that remains the courts function in civil trials and the jurys function in criminal trials. If admitted, the evidence should be subject to test in the usual fashion.Responding for the government, minister for the future digital economy and online safety Baroness Margaret Jones, said, We are agreed that we must prevent future miscarriages of justice. We fully understand the intention and the significance of the issue. We are actively considering this matter and will announce next steps in the new year.Well, here we are, Happy New Year. I imagine we all hope the government will make such an announcement with urgency.Read more about the use of computer evidence in courtsChange to rules on computer evidence will be an outcome of Post Office scandal - The executive currently heading up the Post Offices investigations department has told public inquiry that rules on computer evidence have to change.A trial relying on computer evidence should start with a trial of the computer evidence - Learning from the Post Office Horizon scandal - the most widespread miscarriage of justice in recent British legal history.More than 900 subpostmaster convictions wouldnt have happened without Post Office-backed law change - IT expert says it cannot be the case that computer evidence is treated as accurate in court, without investigation into surrounding circumstances.