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The Horizon of private prosecutions: The post-Post Office inquiry



United Kingdom

A House of Commons inquiry into convictions of sub-postmasters who may have been wrongly convicted for unexplained losses in branch accounts is likely to reinforce the importance of appointing independent investigators and full cooperation from alleged victims in private prosecutions.

  On 7 July 2020, a House of Commons scrutiny committee heard evidence of whether there are sufficient safeguards in place to prevent miscarriages of justice in private prosecutions.

The inquiry will focus on the circumstances where an organisation is allowed to act as a prosecutor when it is also the victim and investigator of an alleged offence.

The Justice Committee set up the inquiry following a request from the Criminal Cases Review Commission, which recently referred 47 convictions of employees of the Post Office for appeal.

Post Office investigation

The Commission’s referrals were made as a result of an abuse of process argument concerning issues with the Post Office’s Horizon computer system, which may have had an impact on the safety of the convictions.

The Post Office brought hundreds of private prosecutions against sub-postmasters who had unexplained losses in their branch accounts.

A recent trial in the High Court found that shortfalls in the accounts may have been as a result of errors in the Horizon accounting system, introduced by the Post Office in 2000.

Because the Post Office relied on evidence produced by the faulty Horizon system, hundreds of sub-postmasters may have been wrongly convicted of crimes they did not commit. 

Safeguards in private prosecutions

Private prosecutors are not legally required to abide by the Code for Crown Prosecutors, or the CPS Full Code Test. However, the CPS Legal Guidance on Private Prosecutions does state that a private prosecution should be taken over and stopped by the CPS, if the evidential stage or the public interest stage of the CPS Full Code Test are not met. 

Lawyers are therefore likely to advise against bringing, or continuing with, a private prosecution if the evidential and public interest tests have not been satisfied.   

In some cases, the private prosecutor must seek the consent of the Attorney General or the DPP before commencing proceedings.

Private prosecutions will be closely scrutinised by defence solicitors, who can refer matters to the CPS for review. Defence solicitors can also raise evidential issues and concerns about the fairness of proceedings through the court. This could result in an argument for an abuse of process. 

In 2019, the Private Prosecutions Association (PPA) introduced the Code for Crown Prosecutors. Adherence to the code is voluntary but members of the PPA (including Fieldfisher) confirm they will abide by it. 

The aim of the code is to provide a benchmark for best practice in the conduct of private prosecutions. It requires investigators to comply with the requirement of paragraph 3.5 of the Criminal Procedure and Investigations Act 1996 Code of Practice, which states that investigators are to pursue all reasonable lines of enquiry, whether these point towards or away from the suspect.

The code also states that prosecutors must be satisfied that the facts alleged amount to a prima facie case.


There is a real risk that organisations who bring a private prosecution will encounter a conflict of interest that could call into question their ability to conduct an objective investigation and prosecution. 

It is often advisable for organisations to instruct independent investigators to assist with the investigation process, particularly in complex matters. 

This will help to ensure a degree of impartiality and that the investigation is conducted properly. 
However, investigators and prosecutors are only able to evaluate the case based on evidence that has been made available to them.

If an organisation decides to withhold certain evidence from investigators or instructed lawyers, this could have a detrimental effect on the impartiality of any subsequent prosecution and the fairness of those proceedings. 
This will no doubt be a cause for concern during the inquiry. 

For more information on our private prosecutions service, please contact a member of the FCCI team.

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