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CPS Guidance for Experts on Disclosure, Unused Material and Case Management

updated 30/9/19|Legal Guidance

CPS Guidance for Experts on Disclosure, Unused Material and Case Management


The instructions contained in this guidance are designed to provide a practical guide to preparing expert evidence and to provide guidance on the disclosure obligations of expert witnesses instructed by the investigator and/or the Crown Prosecution Service (the Prosecution Team). These instructions will assist expert witnesses, investigators and prosecutors to perform their duties effectively fairly and justly, which is vitally important to the integrity of the criminal justice system.

The considered application of this guidance and appropriate management of the materials within the investigation by experts will enhance their credibility and promote confidence in the role of the expert witness within the prosecution process.

This guidance reflects the commitment of the Prosecution Team to working alongside expert witnesses and other agencies to ensure that case management and disclosure requirements are complied with fairly and properly.

1. Introduction

1.1 You are instructed by the Prosecution Team, which comprises the Police (or another investigator) and the Crown Prosecution Service, as an expert in this investigation. It is important that you understand the obligations placed upon you by this status. As an expert witness you have an overriding duty to assist the court and in this respect, your duty is to the court and not to the Prosecution Team instructing you. This will include obligations relating to the disclosure of unused material.

1.2 The word disclosure is often used in criminal proceedings to refer to the disclosure of unused material but experts in criminal proceedings have a number of different obligations as to disclosure.

1.3 Defence and prosecution experts are subject to the obligations contained in the Criminal Procedure Rules both in part 3 as to case management and part 19 as to expert evidence. Further guidance for all experts is contained in the 2015 Criminal Practice Direction that expands upon the Criminal Procedure Rules. These provisions oblige all experts to disclose certain information about themselves and their work.

1.4 Prosecution experts have further obligations as to the disclosure of unused material.

1.5 The obligations as to unused material which apply to you as a prosecution expert assist in ensuring that the Prosecution Team can comply fully with their disclosure obligations. The prosecution must disclose to the accused any prosecution material which might reasonably be considered capable of undermining the case for the prosecution against the accusedor of assisting the case for the accused. This obligation takes precedence over any internal codes of practice or other standards set by any professional organisations to which you may belong. Your obligations as to the disclosure of unused material are set out in part four of this guidance but can be summarised in the key actions of retain, record and reveal.

1.6 A failure to comply with these guidelines may have a number of adverse consequences which could include:

  • A prosecution being halted or delayed;
  • The appellate courts finding that a conviction is unsafe;
  • The tribunal making an adverse judicial comment about you as an expert. Such an adverse judicial comment could seriously undermine your credibility as an expert and consequently your fitness to be instructed in future cases;
  • Professional embarrassment, including possible action by a professional body, loss of accreditation and the potential for civil action by an accused

1.7 Conversely, your credibility as an expert will be enhanced by the considered application of this guidance and your appropriate management of the materials within the investigation.

2. Criminal Procedure Rules: the Overriding Objective

2.1The overriding objective, which is at the heart of the Criminal Procedure Rules (CrimPR), is that criminal cases be dealt with justly.

2.2 The presumption of innocence and a robust adversarial process are essential features of the legal tradition in England and Wales and of the defendants right to a fair trial. The overriding objective acknowledges those rights. It is not justice that questions of guilt or innocence are determined by procedural manoeuvres. On the contrary, justice is best served when the issues between the parties are identified as early and as clearly as possible.

2.3 All participants have a duty to deal with cases justly. Participants must ensure that they take or do any step which furthers the overriding objective. This means taking positive action to identify to the parties and the court any significant failure which will hinder the trial process. This duty extends to co-operating with each other and the court.

2.4 A participant is anyone who is involved in any way with the case. This includes the parties to the proceedings (the prosecuting authority and defendant) and extends to others such as the police, witnesses (prosecution and defence), experts, defence representatives, court staff, and judges.

2.5 Participants in criminal proceedings must actively assist the court in furthering the overriding objective by complying with the case management process set out in CrimPR 3.1 and 3.11. For expert witnesses this includes informing the court and those instructing them of any difficulties in complying with court directions and dates set by the court.

3. The disclosure obligations of all expert witnesses

3.1 Expert witnesses, whether instructed by the defence or the prosecution, are subject to a number of obligations to disclose information and material when preparing statements or reports for use in criminal proceedings. Some examples of those obligations are set out in this guidance but this is not intended to be a comprehensive guide to the obligations of an expert witness. It is the responsibility of those providing expert evidence to ensure they have an accurate understanding of the requirements of the criminal justice system and to meet those requirements. Further guidance on the obligations of expert witnesses has been provided by the office of the Forensic Science Regulator and can be found at:

3.2 Part 19 of the Criminal Procedure Rules (CrimPR 19)

3.2.1 The Criminal Procedure Rules (CrimPR) are updated regularly and the current version is to be found at The details set out below are taken from the Rules as at 1 September 2019.

3.2.2 CrimPR 19.2 provides that an expert must help the court to achieve the overriding objective:

  • by giving opinion which is objective and unbiased,
  • within the experts area of expertise,
  • by complying with directions made by the court,
  • by informing the court of any significant failure to take any step required by such a direction,
  • by informing all parties if their opinion changes from that contained in an earlier report.

3.2.3 CrimPR 19.2(3)(d) also obliges all experts to disclose to the party instructing them anything (of which the expert is aware) that might reasonably be thought capable of undermining the expert’s opinion or detract from the credibility or impartiality of the expert (for further guidance see paragraph 3.3.2 and 3.3.3below).

3.2.4 When an expert prepares a report for service under CrimPR 19.3(3) that report must contain all the matters set out in CrimPR 19.4. Note that the provisions of CrimPR 19.4 do not apply to a summary of an experts conclusions served under CrimPR 19.3(1) generally known as a Streamlined Forensic Report or SFR1. CrimPR 19.4 requires:

(a) details of the experts qualifications, relevant experience and accreditation;

(b) details of any literature or other information which the expert has relied on in making the report;

(c) a statement setting out the substance of all facts given to the expert which are material to the opinions expressed in the report, or upon which those opinions are based;

(d) that the expert makes clear which of the facts stated in the report are within the experts own knowledge;

(e) where the expert has based an opinion or inference on a representation of fact or opinion made by another person for the purposes of criminal proceedings (for example, as to the outcome of an examination, measurement, test or experiment);(i) identify the person who made that representation to the expert, (ii) give the qualifications, relevant experience and any accreditation of that person, and (iii) certify that that person had personal knowledge of the matters stated in that representation;

(f) where there is a range of opinion on the matters dealt with in the report (i) summarise the range of opinion, and (ii) give reasons for the experts own opinion;

(g) if the expert is not able to give an opinion without qualification, state the qualification;

(h) such information as the court may need to decide whether the experts opinion is sufficiently reliable to be admissible as evidence;

(i) a summary of the conclusions reached;

(j) contain a statement that the expert understands an experts duty to the court, and has complied and will continue to comply with that duty; and

(k) the same declaration of truth as a witness statement

3.2.5 When an experts report has been served under CrimPR 19.3(3) then they may also be asked to disclose their working notes. CrimPR 19.3(3)(d) provides that if another party so requires they should be given a copy of or a reasonable opportunity to inspect a record of any examination measurement test or experiment on which an experts findings and opinions were based or that were carried out in in the course of making those findings and opinions AND anything on which any such examination measurement test or experiment was carried out.

3.3 The Criminal Practice Direction Division V Evidence 19A- C

3.3.1 The Criminal Practice Directions Division V make further provision as to expert evidence supplementing and expanding upon some of the provisions of the Criminal Procedure Rules. Full details are at: The details below are up to date as of 1 September 2019.

3.3.2 The Directions include at CPD V evidence 19A examples of the information under CrimPR 19.2(3)(d) that experts should disclose to the party instructing them, that might reasonably be thought capable of undermining the experts opinion or detracting from the credibility or impartiality of the expert (of which the expert is aware). These provisions apply both to summaries of an experts conclusions served under CrimPR 19.3(2) generally known as a Streamlined Forensic Report or SFR1 as well as reports served under CrimPR 19.3(3) and CrimPR 19.4.

3.3.3 In addition to providing guidance at CPD V 19A.8 and 19.9 on what experts are reasonably expected to be aware of , CPD V 19A.7 provides examples of information that should be disclosed by all experts under CrimPR 19.2(3)(d) including:

any fee arrangement under which the amount or payment of the experts fees is in any way dependent on the outcome of the case;

any conflict of interest of any kind, other than a potential conflict disclosed in the experts report;

adverse judicial comment;

  • any case in which an appeal has been allowed by reason of a deficiency in the experts evidence;
  • any adverse finding, disciplinary proceedings or other criticism by a professional, regulatory or registration body or authority, including the Forensic Science Regulator;
  • any such adverse finding or disciplinary proceedings against, or other such criticism of, others associated with the corporation or other body with which the expert works which calls into question the quality of that corporation's or body's work generally;
  • conviction of a criminal offence in circumstances that suggest:
    1. a lack of respect for, or understanding of, the interests of the criminal justice system (for example, perjury; acts perverting or tending to pervert the course of public justice),
    2. dishonesty (for example, theft or fraud), or
    3. a lack of personal integrity (for example, corruption or a sexual offence);
  • lack of an accreditation or other commitment to prescribed standards where that might be expected;
  • a history of failure or poor performance in quality or proficiency assessments;
  • a history of lax or inadequate scientific methods;
  • a history of failure to observe recognised standards in the expert’s area of expertise;
  • a history of failure to adhere to the standards expected of an expert witness in the criminal justice system.

3.3.4 The Criminal Practice Direction (CPD V Evidence 19B) also sets out the declaration that should appear) in any report served under CrimPR 19.3(3) if not in these words, in substantially the same terms. Point 14 of 3.3.5 applies only to prosecution experts. These provisions do not apply to a summary of an experts conclusions served under CrimPR 19.3(2) generally known as a Streamlined Forensic Report or SFR1.

3.3.5 The suggested declaration at CPD V 19B includes the following:

  • I understand that my duty is to help the court to achieve the overriding objective by giving independent assistance by way of objective, unbiased opinion on matters within my expertise, both in preparing reports and giving oral evidence. I understand that this duty overrides any obligation to the party by whom I am engaged or the person who has paid or is liable to pay me. I confirm that I have complied with and will continue to comply with that duty.
  • I confirm that I have not entered into any arrangement where the amount or payment of my fees is in any way dependent on the outcome of the case.
  • I know of no conflict of interest of any kind, other than any which I have disclosed in my report.
  • I do not consider that any interest which I have disclosed affects my suitability as an expert witness on any issues on which I have given evidence.
  • I will advise the party by whom I am instructed if, between the date of my report and the trial, there is any change in circumstances which affect my answers to points 3 and 4 above.
  • I have shown the sources of all information I have used.
  • I have exercised reasonable care and skill in order to be accurate and complete in preparing this report.
  • I have endeavoured to include in my report those matters, of which I have knowledge or of which I have been made aware, that might adversely affect the validity of my opinion. I have clearly stated any qualifications to my opinion.
  • I have not, without forming an independent view, included or excluded anything which has been suggested to me by others including my instructing lawyers.
  • I will notify those instructing me immediately and confirm in writing if for any reason my existing report requires any correction or qualification.
  • I understand that: (a) my report will form the evidence to be given under oath or affirmation; (b) the court may at any stage direct a discussion to take place between experts; (c) the court may direct that, following a discussion between the experts, a statement should be prepared showing those issues which are agreed and those issues which are not agreed, together with the reasons; (d) I may be required to attend court to be cross-examined on my report by a cross-examiner assisted by an expert. (e) I am likely to be the subject of public adverse criticism by the judge if the Court concludes that I have not taken reasonable care in trying to meet the standards set out above.
  • I have read Part 19 of the Criminal Procedure Rules and I have complied with its requirements.
  • I confirm that I have acted in accordance with the code of practice or conduct for experts of my discipline, namely [identify the code]
  • [For Experts instructed by the Prosecution only] I confirm that I have read guidance contained in a booklet known as Disclosure: Experts’ Evidence and Unused Material which details my role and documents my responsibilities, in relation to revelation as an expert witness. I have followed the guidance and recognise the continuing nature of my responsibilities of disclosure. In accordance with my duties of disclosure, as documented in the guidance booklet, I confirm that: (a) I have complied with my duties to record, retain and reveal material in accordance with the Criminal Procedure and Investigations Act 1996, as amended; (b) I have compiled an Index of all material. I will ensure that the Index is updated in the event I am provided with or generate additional material; (c) in the event my opinion changes on any material issue, I will inform the investigating officer, as soon as reasonably practicable and give reasons.

I confirm that the contents of this report are true to the best of my knowledge and belief and that I make this report knowing that, if it is tendered in evidence, I would be liable to prosecution if I have wilfully stated anything which I know to be false or that I do not believe to be true

3.3.6 The Criminal Practice Direction provides further guidance on pre-hearing discussions of expert evidence that should be followed when such discussions are held. See CPD V Evidence 19C.

4. The disclosure obligations of prosecution experts

4.1 In addition to the disclosure obligations that apply to all expert witnesses, experts instructed by the prosecution are subject to further obligations as to unused material.

4.2 Unused material is relevant material that is not used as evidence. During the course of any investigation material is generated. Some of it is used as evidence and other material is not used. The material that is not used as evidence is known as unused material. Unused material is material that is relevant to the investigation but which does not actually form part of the case for the prosecution against the accused. Even though the material may not be used as evidence, it is important that for the purposes of disclosure this material is recorded, retained and where necessary revealed to the defence.

4.3 The CPS Disclosure Manual (the Manual) contains operational instructions on disclosure which have been issued by the CPS. It explains how the Prosecution Team have agreed to fulfil their duties to disclose unused material to the defence. These duties arise under statute and at common law. The Manual contains practical guidance to the police and CPS practitioners which supplements the framework of the Criminal Procedure and Investigations Act 1996 (CPIA), the Code of Practice and the Attorney Generals Guidelines. The Manual and the Guidelines can be found at: CPS Disclosure Manual and Attorney General's Guidelines on Disclosure 2013

4.4 The disclosure of unused material is governed primarily by the CPIA ( and the Code issued under it. There are other obligations as to unused material on the prosecution that apply after any conviction and in the early stages of a criminal case when the CPIA may not apply. More details are available in the CPS Disclosure Manual and the Attorney General's Guidelines on Disclosure 2013

4.5 The CPIA provides that the prosecution must disclose to the accused any prosecution material which might reasonably be considered capable of undermining the case for the prosecution against the accused or of assisting the case for the accused (the disclosure test).

4.6 The CPIA codes of practice provide that in conducting an investigation, investigators 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. Experts should also have regard to information that points away from, as well as towards the suspect.

4.7 There are three key obligations arising for you, as an expert, as the investigation progresses in order to discharge your obligations. Your understanding of these and your delivery of them is the key to you adequately fulfilling your disclosure obligations. The relevant steps are to retain, to record, and to reveal.

4.8 Retain

4.8.1 What to retain.You should retain everything, including physical, written and electronically captured material, until otherwise instructed and the investigator has indicated the appropriate action to take.

4.8.2 How long to retain. The period of time for which materials are required to be retained will vary from case to case and will depend on a number of factors. Examples include the nature of the offence; the stage and status of any legal proceedings; whether the case is of special interest. It must also be remembered that the retention requirement may alter as a result of a change of circumstances during the course of the investigation. You should, therefore, obtain advice from the investigator for the retention period that applies to this particular investigation and always before contemplating destruction of any material.

4.9 Record

4.9.1 When to record. The requirement for you to commence making records begins at the time you receive instructions and continues for the entirityof the time you are involved.  Circumstances may exist, however, where practitioners should commence making records, in accordance with this guidance, prior to any instructions from the police. Examples of this would be:

  • where, as a pathologist the outcome of a routine post-mortem suggests to you that death has been caused under suspicious circumstances;
  • as a medical practitioner you find injuries that are not consistent with the alleged cause;
  • as a fire scene examiner you believe a fire to have been started deliberately.

4.9.2 In all these examples the criminal investigation will start after the practitioners original involvement but the results of the previous examinations will almost certainly be material to any investigation and subsequent prosecution. The list above is not intended to be exhaustive. If you have any doubts, start recording,

4.9.3 What to record. You should keep records of all the work you have carried out and any findings you make in relation to the investigation. The guidance provided below reflects best practice and your records, as a minimum, should contain information relating to:

  • the collection and movement of items, including:
  • the date on which you take or receive material (physical items and information);
  • and the date of subsequent movement of the material to another party;
  • from who or where and to whom or where material is moved;
  • the means by which you receive or pass material from/to another party;
  • the examination of materials;
  • your notes, and those of any assistant, should be signed, dated, attributable to the individual and produced contemporaneously, whenever practicable;
  • the notes should be sufficiently detailed and expressed in such a manner that another expert in your field can follow the nature of the work undertaken;
  • any assumptions made and the inferences you have drawn from the work;
  • verbal and other communications;
  • you should keep your own notes of all meetings you attend;
  • you should keep your own notes of telephone conversations and it is important that points of agreement, or disagreement and agreed actions are recorded;
  • you should ensure that a record of all emails and other electronic transmissions (such as images), sent or received, is kept;
  • you should keep clear notes of any witness accounts or explanations that you have been provided with, or any other information received.

4.9.4 How to record. The media you use for making your records should be capable of meeting all the requirements given above, be durable and provide a reliable means of retrieval. Your notes, in whatever form, should also be structured in a manner that facilitates review, whilst complying with any necessary security requirements. Any updates, alterations or comments should be clear. It is important that your notes are clear and comprehensive. This will allow another person who may subsequently review them to have a full understanding of the position at any given time.

4.10 Revealing unused material

4.10.1 What to reveal. You are required to reveal everything you have recorded to the Prosecution Team. It is a necessary and important part of your disclosure obligations to make the Prosecution Team aware of all the material you have in your possession in relation to the investigation. This will then enable them to make informed decisions as to what material is relevant, and then what material satisfies the disclosure test. Revealing material to the prosecution team does not necessarily mean disclosure to the defence.

4.10.2 When to reveal. Parts 2 and 3 of this guidance set out the obligations of all experts under the Criminal Procedure Rules and the Criminal Practice Direction to disclose or reveal the information referred to there. Unused material that has been recorded under paragraph 4.9 above should be provided to the Prosecution Team when a report is provided under CrimPR 19.3(3) and CrimPR 19.4 (not when a summary of an expert’s conclusions served under CrimPR 19.3(2) generally known as a Streamlined Forensic Report or SFR1 is prepared and served).

4.10.3 How to reveal. Unused material that has been recorded under paragraph 4.9 should be revealed to the Prosecution Team by completing an index of unused material (the Index). Experts employed by the police are not a third party under the CPIA, are already required to comply with the CPIA 1996 and should comply with the detailed guidance in the CPS Disclosure Manual.

4.10.4 The Index of Unused Material. In order to reveal material to the Prosecution Team, it is necessary that you describe all the unused material in your possession. All the material not identified in your report/statement should be placed on the Index.

4.10.5 The Index is designed to enable you to provide to the Prosecution Team a description of all the unused material in your possession in a structured, comprehensive and informative manner.

4.10.6 An example of a specimen Index is given in Appendix A. You will need to tailor the descriptions of the materials to meet your specific case requirements. Your descriptions, however, must be full enough for others to clearly understand the nature of the material. Please note that this example is neither exhaustive nor exclusive.

4.10.7 You should not attempt to make judgements on the significance of material when producing the Index. Where you believe material may be confidential or sensitive, then this should be placed on a separate schedule and discussed with the Prosecution Team.

4.11 Declaration of Understanding

4.11.1 Prosecution experts are required to confirm their understanding of their disclosure obligations to the court as set out in this guidance by signing the declaration for prosecution experts contained in the Criminal Practice Direction V Evidence 19B at point 14, set out in paragraph 3.3.5 of this guidance.

5. The Experts self-certificate

5.1 Upon receipt of instructions you are required to complete a self-certificate (the Certificate) in every case that you are instructed as an expert witness for the Prosecution. The completed Certificate should be sent to the disclosure officer or investigating officer. The Certificate can be found at Appendix B.

6. Streamlined Forensic Reporting and Disclosure of Unused

6.1 The purpose of Streamlined Forensic Reporting is to identify the key issues in the case at the earliest opportunity, and hence ensure forensic evidence is targeted at these issues, and only these issues, as soon as possible.

6.2 The Criminal Procedure Rules refer to Streamlined Forensic Reports at CrimPR 19.3(3)(1) as a summary of an experts conclusions. Such summaries will not always be completed by experts but often by others on the basis of an experts initial findings.

6.3 The first Streamlined Forensic Report (SFR 1) is not an experts report under CrimPR 19.3(3) and is not subject to the requirements of CrimPR 19.4 (see paragraph 3.2.5) or CPD V Evidence 19B (paragraph 3.3.4). The obligations to provide an experts index of unused material as set out in part 4 of this guidance does not apply at the point an SFR 1/summary of an experts conclusions is served.

7. Queries

If you have any queries relating to the contents of this guidance, please contact the investigating officer, the disclosure officer or the prosecutor.

Appendix A: Experts index of unused material

Download the Experts index of unused material here (Word doc, approx 20kb)

Appendix B: Expert witnesses self-certificate

Download the Expert witnesses self-certificate here (Word doc, approx 18kb)

PDF edition of this Guidance Booklet for Experts

Download a PDF edition of the guidance here (approx 271kb).

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