Investigators who are tasked with obtaining evidence that might be used in a private prosecution should seek, where possible, to comply with the same codes of practice and guidance as apply to law enforcement investigators to ensure that (1) any evidence obtained is admissible; (2) the investigation is fair and balanced; and (3) the proceedings are not an abuse of the Court’s process.


The person in charge of an investigation must ensure that proper procedures are in place for recording, retaining and revealing (to those acting on behalf of the private prosecutor) material obtained in the criminal investigation which may be relevant. Private prosecutors should be aware of the need to record relevant information as soon as practicable after the time it is obtained.


Private prosecutors should also consider their obligations under the Data Protection Act 2018 (DPA 2018) and the lawful basis for processing personal data. Private prosecutors will need to consider the specific provisions that apply to special category data. Private prosecutors should bear in mind that they are unlikely to be a “competent authority” for the purposes of Part 3 of the DPA 2018.


The records of the investigation should also address compliance with the GDPR in terms of the use of personal data. The undertaking of a privacy impact assessment in relation to the investigation as a whole would be best practice.


Independence & impartiality


Investigations by and for private prosecutors should be conducted impartially, objectively and independently.


In conducting an investigation, the investigator should comply with paragraph 3.5 of the CPIA Code of Practice:

“In conducting an investigation, the investigator should pursue all reasonable lines of inquiry, whether these point towards or away from the suspect. What is reasonable in each case will depend on the particular circumstances. For example, where material is held on computer, it is a matter for the investigator to decide which material on the computer it is reasonable to inquire into, and in what manner.”


Terms of reference


The investigator(s) should at the outset agree with the prosecution written terms of reference regarding the scope of the investigation.


Digital evidence


The investigator(s) should keep accurate records of how and by whom digital evidence was gathered, retained and prepared, as well as any search terms and the review methodology applied. The ACPO Good Practice Guide for Digital Evidence and the Attorney General’s Guidelines on Disclosure should be followed where applicable.


Interviews with suspects


Whilst many private prosecutors will not conduct interviews with suspects, those that do should comply with the PACE Codes of Practice to the extent that they are applicable. Private prosecutors should have particular regard to:

  1. Code C: Code of Practice for the Detention, Treatment and Questioning of Persons by Police Officers. Parts 10, 11 and 13 contain provisions for the conduct of interviews with suspects.
  2. PACE Codes E and F deal with the audio and video recording of interviews with suspects.


In principle, there is no restriction on a suspect being invited to attend an interview. However, a private prosecutor should not suggest that an adverse inference might be drawn from any failure to attend or answer questions.3 A suspect must be told that they do not have to answer any questions, that they are free to leave at any time, that they are entitled to take legal advice and that anything they do say may be given/used in evidence against them.


Interviews with witnesses


It is best practice for witness statements to be taken by experienced investigators or litigators. A full record should be kept of all contact with potential witnesses.


All normal rules of criminal procedure apply to a private prosecutor and should be observed, including the obligation to produce witness statements on the standard template, and to retain any drafts of witness statements, notes of interview and transcripts.


Assistance from the Court – the duty of full and frank disclosure


Should a private prosecutor seek the assistance of the Court to obtain material, the fundamental duty of candour must be observed in any application.


The prosecutor has a duty of full and frank disclosure which necessarily includes a duty not to mislead the judge and which requires disclosure to the Court of any material that is potentially adverse to the application, which might militate against it or which may be relevant to the judge’s decision.


Privacy, surveillance and covert activities


Investigators gathering evidence in support of a private prosecution do not fall under the categories of agencies with investigative powers under the Regulation of Investigatory Powers Act 2000 (“RIPA”) or the Investigatory Powers Act 2016. However, private prosecutors should have regard to all relevant legislation in commissioning or undertaking any covert activity, and document any decisions taken to commence surveillance. Private prosecutors should be aware that certain forms of surveillance that are available to public authorities are not available to private investigators. Their use may constitute a criminal offence.


A written record should be kept of the decision to commence covert investigations, the rationale behind that decision, the tactics employed and the scope and boundaries of the investigation, in advance of surveillance or other covert activity being conducted. A decision log should be kept as the case progresses, so that the legality, necessity and proportionality of the investigation can be considered at all times.


The document should address collateral intrusion, and the management of material involving third parties that is obtained during the course of surveillance, including the secure disposal of such material.


Co-operation with law enforcement


Some private prosecutors seek assistance from police forces to obtain evidence and conduct investigations.


If any agreement has been reached with the police force for the private prosecutor to make a contribution to the police costs of investigation, the details of this agreement should be disclosed to the defence.

2 An exception would be where the private prosecutor is “charged with the duty of investigating offences or charging offenders as it applies in relation to questioning by constables” in accordance with s34(4) of the Criminal Justice and Public Order Act 1994. Blackstones Criminal Practice (at D1.3) provides examples of cases in which persons other than constables have been held to be “charged with the duty of investigating offences” in this context.

PPA Code for Private Prosecutors edition 1.1 revised 30.07.19