On Friday 23 April 2021, the Court of Appeal (Criminal Division) comprising Holroyde LJ, Picken & Farbey JJ (all Middle Temple Benchers), handed down judgment in the 42 conjoined appeals against conviction (R v Hamilton & others [2021] EWCA Crim 577). Whilst the quashing of 39 of the 42 convictions on grounds of abuse of process did not come as any great surprise, given the outcome of the earlier High Court litigation and the approach taken by the Post Office to the Criminal Cases Review Commission (CCRC) referrals, the extent of the disclosure failings were, on any view, remarkable and very concerning. Indeed, it serves as a salutary reminder that it should never be assumed that computerised records are always accurate. Following on from the judgment in Hamilton & others there are now a raft of applications for leave to appeal (with many more potentially in the wings). It is therefore likely that the Hamilton & others judgment will not be the last word on this matter. Master Tom Little considers the judgment, its ramifications, what will happen next and the lessons to be learnt from it for those conducting criminal litigation. 


Over a period between 2003 and 2013 the 42 appellants, who had all been employees of the Post Office, were either convicted of, or pleaded guilty to, offences committed between 2000 and 2012. The appellants were sub-postmasters who ran their respective branches. The Post Office acted as a private prosecutor in all the cases. The appellants were variously charged with offences of theft, fraud and false accounting. In most of the cases Horizon, the electronic point of sale and accounting computer system used in branch Post Offices, showed a shortfall in the accounts of the branches where the employees worked. Horizon recorded all transactions at the branch. It calculated how much cash and stock there should be. From an early stage, employees had reported discrepancies in their accounts which they considered were caused by faults in Horizon. They generally did so to a helpline. Despite these difficulties, the Post Office maintained for many years that Horizon was reliable and not to be doubted, despite the increasing evidence that there were problems. The Post Office maintained a position that the shortfalls were, and could only be, the result of dishonesty or carelessness on the part of their employees and indeed went on to prosecute them as a result. The Post Office required employees to repay the shortfall. Some did so using their own money; some resorted to the commission of criminal offences. In 2012, the Post Office commissioned an independent review which found systemic problems with Horizon. In civil litigation brought by employees against the Post Office ([2019] EWHC 3408 (QB), [2019] 12 WLUK 208), the High Court found inter alia that the Post Office had failed to investigate or disclose problems with Horizon. The findings of Fraser J in that civil litigation formed the basis of the factual circumstances upon which the Court of Appeal proceeded to consider whether the prosecutions amounted to an abuse of process and on what basis. The Post Office accepted in four cases that the prosecution had been an abuse of process because a fair trial had been rendered impossible (category one abuse) and because it was an affront to the public conscience (category two abuse). In a further 35 cases, it accepted that there had been a category one abuse but not a category two abuse. In the remaining three cases, it resisted the appeal on the ground that the reliability of Horizon was not essential to its case.


It is well understood that there are two separate (and normally distinct) categories of abuse of process which merit the staying of a case in the Crown Court as an abuse of process. First, the impossibility of a fair trial. Second, the unconscionability of the particular prosecution, bearing in mind the circumstances of the case and prosecution. On the facts, the Court concluded that it was not necessary for any appellant alleging category two abuse to prove misconduct going beyond that which was established as (and accepted to be) category one abuse. The Court concluded that the Post Office’s failings directly implicated the Courts and therefore engaged category two. The problems with the Horizon system were known by the Post Office. There was therefore a failure both to investigate and disclose. Had a complete picture been disclosed, then the Court of Appeal concluded that no prosecution would have taken the course that it had. Indeed, the failures were so egregious as to make the prosecution of any of the Horizon cases as an affront to the conscience of the Court. Where there was no independent evidence of an actual shortfall, then Horizon would have been essential to the prosecution and all such cases (even where there were guilty pleas), were not just category one abuse but also category two. However, in three of the appeals, the reliability of Horizon evidence had not been essential to the prosecution case and those three appeals were dismissed.


Aside from the obvious and important correction of the significant number of past miscarriages of justice (including those that followed guilty pleas), these cases act as a salutary warning of the importance of the golden rule of disclosure, how reasonable lines of inquiry must be followed and that if they are not then their consequences can be significant. Those who prosecute are familiar with their disclosure obligations. That can and does involve asking difficult and probing questions (sometimes more than once). That position is potentially more acute in a private prosecution. In the last five years, there has been a marked increase in the number of private prosecutions by a wide range of bodies and institutions. Many of those prosecutions relate to allegations of dishonesty. The judgment in Hamilton & others is likely to cause those defending in private prosecutions to focus even more clearly on the particular approach that was taken to disclosure and the need to have followed all reasonable lines of inquiry.

Where the private prosecutor acts as both investigator and prosecutor, the risk of a blinkered approach to disclosure (or worse) is manifest. Where the evidence relied upon is obtained from computers, it is likely that complaints as to the reliability of such information, and which might previously have been treated as something of a red herring, may be given greater credence (initially at least). Equally, those prosecuting private prosecutions will need to review their ongoing cases to make sure that a correct and proper approach has been taken to disclosure. However, the ramifications of the failures here go potentially beyond private prosecutions and the assumption that computer systems are flawless. Many prosecutions for offences of dishonesty involve evidence obtained from computers. In the vast majority of those cases, the evidence is entirely accurate and reliable. However, where any defendant raises any issue as to reliability or denies that they have acted dishonestly (but cannot explain the data obtained), then consideration should be given by those investigating as to reliability of that data. It is perhaps though also worth making the point that despite the egregious failures that did arise, the Court will need to be astute in the future to ensure that convictions that were safe and were the result of dishonest conduct are not taken advantage of. In reality, this will mean a sharp focus on whether the Horizon data really was essential or not and in particular what other evidence there was. 

Despite the publicity which these cases received it is important to observe that the judgment in Hamilton & others does not mark a discernible change as to the law of abuse of process. The threshold remains a very high one as the Court stressed. These were exceptional circumstances, hence meriting such a large number of convictions being quashed.

The future

Earlier this year more than 500 former sub-postmasters who were convicted at the material time were written to and invited to consider whether any miscarriage of justice occurred in their case. This brings with it the possibility of a flood of appeals. In July 2021, the Court of Appeal held a directions hearing in a large number of new applications for leave to appeal against conviction in these so called ‘Post Office’ cases. A limited number of those applications include prosecutions that, for particular reasons, were not brought by the Post Office but by the Crown Prosecution Service. It will remain to be seen whether that will make any difference to any of the abuse of process arguments. Following on from the judgment in Hamilton & others, the extent to which Horizon really was essential may become an important factual dispute and one which it may be difficult (all these years later) to establish one way or the other, leaving the Court of Appeal to have to make that decision on the evidence put before it. 

Master Tom Little

Master Tom Little is Senior Treasury Counsel at the Central Criminal Court. As well as prosecuting the full range of homicide, terrorism and sexual offences he is currently instructed on behalf of the Crown Prosecution Service to respond to all applications for leave to appeal from sub-postmasters in cases where the CPS (as opposed to the Post Office) were the prosecutor.

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