Posted: 05 / 04 / 2020

Part 19 of the Criminal Procedure Rules 2015 dealing with expert evidence in Crown Courts and Magistrates’ Courts in England & Wales has been updated with effect from 1 April 2019. For convenience the new materials are brought together in a single document here.

The Criminal Procedure Rules are in future to be referred to by the abbreviation CrimPR to distinguish them from the Civil Procedure Rules, see rule 2.3.(2).


Expert evidence – guide to the amendments to the Rules

Part 19 (Expert evidence) has been amended to include a new rule about an expert witness’ obligations to the court.  At the same time the Criminal Procedure Rules as a whole have been rearranged – the new Part 19 dealing with expert evidence previously appeared as Part 33 of the 2014 edition of the rules.

Rule 19.2 (Expert evidence; Expert’s duty to the court) now requires an expert witness, as part of her or his duty to the court, to help the court in some of the same ways as a party to the case, by complying with directions (for example, as to the time by when a report must be served), and by warning the court of any significant failure to act as required by a direction (for example, by warning of substantial delay in the preparation of a report).

In response to observations by the Court of Appeal in its judgment in R v Reynolds, R v Rosser [2014] EWCA Crim 2205, and in response to reports by Rule Committee members of increasing difficulties in obtaining expert reports within the same times as before, the Committee agreed that an expert’s implicit duty to the court to give a realistic estimate of the time within which expert evidence can be prepared, and to adhere to that estimate, should be made explicit.

A new Rule 19.9 (Expert evidence: Application to withhold evidence from another party), introduced from April 2019, deals with the unusual situation where one party thinks that it would be in the public interest to withhold information from another party, for example information about criminal investigatory techniques.


Expert evidence – the Rules as amended

When this part applies

(1) This Part applies where a party wants to introduce expert opinion evidence.

(2) A reference to an ‘expert’ in this Part is a reference to a person who is required to give or prepare expert evidence for the purpose of criminal proceedings, including evidence required to determine fitness to plead or for the purpose of sentencing.

Expert’s duty to the court


(1) An expert must help the court to achieve the overriding objective —

    (a) by giving opinion which is —
    • (i) objective and unbiased; and
      (ii) within the expert’s area or areas of expertise; and
    (b) by actively assisting the court in fulfilling its duty of case management under rule 3.2, in particular by —
    • (i) complying with directions made by the court, and
      (ii) at once informing the court of any significant failure (by the expert or another) to take any step required by such a direction.

(2) This duty overrides any obligation to the person from whom the expert receives instructions or by whom the expert is paid.

(3) This duty includes obligations —

    (a) to define the expert’s area or areas of expertise —

    • (i) in the expert’s report, and
      (ii) when giving evidence in person;
    (b) when giving evidence in person, to draw the court’s attention to any question to which the answer would be outside the expert’s area or areas of expertise;
    (c) to inform all parties and the court if the expert’s opinion changes from that contained in a report served as evidence or given in a statement; and
    (d) to disclose to the party for whom the expert’s evidence is commissioned anything —

    • (i) of which the expert is aware, and
      (ii) of which that party, if aware of it, would be required to give notice under rule 19.3(3)(c).

Introduction of expert evidence

(1) A party who wants another party to admit as fact a summary of an expert’s conclusions must serve that summary —

    (a) on the court officer and on each party from whom that admission is sought;
    (b) as soon as practicable after the defendant whom it affects pleads not guilty.

(2) A party on whom such a summary is served must —

    (a) serve a response stating —
    • (i) which, if any, of the expert’s conclusions are admitted as fact, and
      (ii) where a conclusion is not admitted, what are the disputed issues concerning that conclusion; and
    (b) serve the response —
    • (i) on the court officer and on the party who served the summary,
      (ii) as soon as practicable, and in any event not more than 14 days after service of the summary.

(3) A party who wants to introduce expert evidence otherwise than as admitted fact must —

    (a) serve a report by the expert which complies with rule 19.4 (Content of expert’s report) on —
    • (i) the court officer, and
      (ii) each other party;
    (b) serve the report as soon as practicable, and in any event with any application in support of which that party relies on that evidence;
    (c) serve with the report notice of anything of which the party serving it is aware which might reasonably be thought capable of –
    • (i) undermining the reliability of the expert’s opinion, or
      (ii) detracting from the credibility or impartiality of the expert;
    (d) if another party so requires, give that party a copy of, or a reasonable opportunity to inspect —
    • (i) a record of any examination, measurement, test or experiment on which the expert’s findings and opinion are based, or that were carried out in the course of reaching those findings and opinion, and
      (ii) anything on which any such examination, measurement, test or experiment was carried out.

(4) Unless the parties otherwise agree or the court directs, a party may not —

    (a) introduce expert evidence if that party has not complied with paragraph (3);
    (b) introduce in evidence an expert report if the expert does not give evidence in person.

Content of expert’s report

Where rule 19.3(3) applies, an expert’s report must —

    (a) give details of the expert’s qualifications, relevant experience and accreditation;
    (b) give details of any literature or other information which the expert has relied on in making the report;
    (c) contain 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) make clear which of the facts stated in the report are within the expert’s own knowledge;
    (e) when 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 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 expert’s own opinion;
    (g) if the expert is not able to give an opinion without qualification, state the qualification;
    (h) include such information as the court may need to decide whether the expert’s opinion is sufficiently reliable to be admissible as evidence;
    (i) contain a summary of the conclusions reached;
    (j) contain a statement that the expert understands an expert’s duty to the court, and has complied and will continue to comply with that duty; and
    (k) contain the same declaration of truth as a witness statement.

Expert to be informed of service of report

A party who serves on another party or on the court a report by an expert must, at once, inform that expert of that fact.

Pre-hearing discussion of expert evidence

(1) This rule applies where more than one party wants to introduce expert evidence.

(2) The court may direct the experts to —

    (a) discuss the expert issues in the proceedings; and
    (b) prepare a statement for the court of the matters on which they agree and disagree, giving their reasons.

(3) Except for that statement, the content of that discussion must not be referred to without the court’s permission.

(4) A party may not introduce expert evidence without the court’s permission if the expert has not complied with a direction under this rule.

Court’s power to direct that evidence is to be given by a single joint expert

(1) Where more than one defendant wants to introduce expert evidence on an issue at trial, the court may direct that the evidence on that issue is to be given by one expert only.

(2) Where the co-defendants cannot agree who should be the expert, the court may —

    (a) select the expert from a list prepared or identified by them; or
    (b) direct that the expert be selected in another way.

Instructions to a single joint expert

(1) Where the court gives a direction under rule 19.7 for a single joint expert to be used, each of the co-defendants may give instructions to the expert.

(2) A co-defendant who gives instructions to the expert must, at the same time, send a copy of the instructions to each other co-defendant.

(3) The court may give directions about —

    (a) the payment of the expert’s fees and expenses; and
    (b) any examination, measurement, test or experiment which the expert wishes to carry out.

(4) The court may, before an expert is instructed, limit the amount that can be paid by way of fees and expenses to the expert.

(5) Unless the court otherwise directs, the instructing co-defendants are jointly and severally liable for the payment of the expert’s fees and expenses.

Application to withhold information from another party

(1) This rule applies where —

    (a) a party introduces expert evidence under rule 19.3(3);
    (b) the evidence omits information which it otherwise might include because the party introducing it thinks that the information ought not to be revealed to another party; and
    (c) the party introducing the evidence wants the court to decide whether it would be in the public interest to withhold that information.

(2) The party who wants to introduce the evidence must —

    (a) apply for such a decision; and
    (b) serve the application on —
    • (i) the court officer, and
      (ii) the other party, but only to the extent that serving it would not reveal what the applicant thinks ought to be withheld.

(3) The application must —

    (a) identify the information;
    (b) explain why the applicant thinks that it would be in the public interest to withhold it; and
    (c) omit from the part of the application that is served on the other party anything that would reveal what the applicant thinks out to be withheld.

(4) Where the applicant serves only part of the application on the other party, the applicant must —

    (a) mark the other part, to show that it is only for the court; and
    (b) in that other part, explain why the applicant has withheld it from the other party.

(5) The court may —

    (a) direct the applicant to serve on the other party any part of the application which has been withheld;
    (b) determine the application at a hearing or without a hearing.

(6) Any hearing of an application to which this rule applies —

    (a) must be in private, unless the court otherwise directs; and
    (b) if the court so directs, may be, wholly or in part, in the absence of the party from whom information has been withheld.

(7) At any hearing of an application to which this rule applies —

    (a) the general rule is that the court must consider, in the following sequence —
      • (i) representations first by the applicant and then by the other party, in both parties’ presence, and then
      • (ii) further representations by the applicant, in the absence of the party from whom information has been withheld; but
    (b) the court may direct other arrangements for the hearing.

Court’s power to vary requirements under this Part

(1) The court may extend (even after it has expired) a time limit under this Part.

(2) A party who wants an extension of time must —

    (a) apply when serving the report, summary or notice for which it is required; and
    (b) explain the delay.


Expert evidence – the Practice Directions

19A.1 Expert opinion evidence is admissible in criminal proceedings at common law if, in summary, (i) it is relevant to a matter in issue in the proceedings; (ii) it is needed to provide the court with information likely to be outside the court’s own knowledge and experience; and (iii) the witness is competent to give that opinion.

19A.2 Legislation relevant to the introduction and admissibility of such evidence includes section 30 of the Criminal Justice Act 1988, which provides that an expert report shall be admissible as evidence in criminal proceedings whether or not the person making it gives oral evidence, but that if he or she does not give oral evidence then the report is admissible only with the leave of the court; and CrimPR Part 19, which in exercise of the powers conferred by section 81 of the Police and Criminal Evidence Act 1984 and section 20 of the Criminal Procedure and Investigations Act 1996 requires the service of expert evidence in advance of trial in the terms required by those rules.

19A.3 In the Law Commission report entitled ‘Expert Evidence in Criminal Proceedings in England and Wales’, report number 325, published in March, 2011, the Commission recommended a statutory test for the admissibility of expert evidence. However, in its response the government declined to legislate. The common law, therefore, remains the source of the criteria by reference to which the court must assess the admissibility and weight of such evidence; and CrimPR 19.4 lists those matters with which an expert’s report must deal, so that the court can conduct an adequate such assessment.

19A.4 In its judgment in R v Dlugosz and Others [2013] EWCA Crim 2, the Court of Appeal observed (at paragraph 11): “It is essential to recall the principle which is applicable, namely in determining the issue of admissibility, the court must be satisfied that there is a sufficiently reliable scientific basis for the evidence to be admitted. If there is then the court leaves the opposing views to be tested before the jury.” Nothing at common law precludes assessment by the court of the reliability of an expert opinion by reference to substantially similar factors to those the Law Commission recommended as conditions of admissibility, and courts are encouraged actively to enquire into such factors.

19A.5 Therefore factors which the court may take into account in determining the reliability of expert opinion, and especially of expert scientific opinion, include:

    (a) the extent and quality of the data on which the expert’s opinion is based, and the validity of the methods by which they were obtained;
    (b) if the expert’s opinion relies on an inference from any findings, whether the opinion properly explains how safe or unsafe the inference is (whether by reference to statistical significance or in other appropriate terms);
    (c) if the expert’s opinion relies on the results of the use of any method (for instance, a test, measurement or survey), whether the opinion takes proper account of matters, such as the degree of precision or margin of uncertainty, affecting the accuracy or reliability of those results;
    (d) the extent to which any material upon which the expert’s opinion is based has been reviewed by others with relevant expertise (for instance, in peer-reviewed publications), and the views of those others on that material;
    (e) the extent to which the expert’s opinion is based on material falling outside the expert’s own field of expertise;
    (f) the completeness of the information which was available to the expert, and whether the expert took account of all relevant information in arriving at the opinion (including information as to the context of any facts to which the opinion relates);
    (g) if there is a range of expert opinion on the matter in question, where in the range the expert’s own opinion lies and whether the expert’s preference has been properly explained; and
    (h) whether the expert’s methods followed established practice in the field and, if they did not, whether the reason for the divergence has been properly explained.

19A.6 In addition, in considering reliability, and especially the reliability of expert scientific opinion, the court should be astute to identify potential flaws in such opinion which detract from its reliability, such as:

    (a) being based on a hypothesis which has not been subjected to sufficient scrutiny (including, where appropriate, experimental or other testing), or which has failed to stand up to scrutiny;
    (b) being based on an unjustifiable assumption;
    (c) being based on flawed data;
    (d) relying on an examination, technique, method or process which was not properly carried out or applied, or was not appropriate for use in the particular case; or
    (e) relying on an inference or conclusion which has not been properly reached.

19A.7 To assist in the assessment described above, CrimPR 19.3(3)(c) requires a party who introduces expert evidence to give notice of anything of which that party is aware which might reasonably be thought capable of undermining the reliability of the expert’s opinion, or detracting from the credibility or impartiality of the expert; and CrimPR 19.2(3)(d) requires the expert to disclose to that party any such matter of which the expert is aware.  Examples of matters that should be disclosed pursuant to those rules include (this is not a comprehensive list), both in relation to the expert and in relation to any corporation or other body with which the expert works, as an employee or in any other capacity:

    (a) any fee arrangement under which the amount or payment of the expert’s fees is in any way dependent on the outcome of the case (see also the declaration required by paragraph 19B.1 of these directions);
    (b) any conflict of interest of any kind, other than a potential conflict disclosed in the expert’s report (see also the declaration required by paragraph 19B.1 of these directions);
    (c) adverse judicial comment;
    (d) any case in which an appeal has been allowed by reason of a deficiency in the expert’s evidence;
    (e) any adverse finding, disciplinary proceedings or other criticism by a professional, regulatory or registration body or authority, including the Forensic Science Regulator;
    (f) 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;
    (g) conviction of a criminal offence in circumstances that suggest;
    • (i) 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),
      (ii) dishonesty (for example, theft or fraud), or
      (iii) a lack of personal integrity (for example, corruption or a sexual offence);
    (h) lack of accreditation or other commitment to prescribed standards where that might be expected;
    (i) a history of failure or poor performance in quality or proficiency assessments;
    (j) a history of lax or inadequate scientific methods;
    (k) a history of failure to observe recognised standards in the expert’s area of expertise;
    (l) a history of failure to adhere to the standards expected of an expert witness in the criminal justice system.

19A.8 In a case in which an expert, or a corporation or body with which the expert works, has been criticised without a full investigation, for example by adverse comment in the course of a judgment, it would be reasonable to expect those criticised to supply information about the conduct and conclusions of any independent investigation into the incident, and to explain what steps, if any, have been taken to address the criticism.

19A.9 The rules require disclosure of that of which the expert, or the party who introduces the expert evidence, is aware.  The rules do not require persistent or disproportionate enquiry, and courts will recognise that there may be occasions on which neither the expert nor the party has been made aware of criticism.  Nevertheless, where matters ostensibly within the scope of the disclosure obligations come to the attention of the court without their disclosure by the party who introduces the evidence then that party, and the expert, should expect a searching examination of the circumstances by the court; and, subject to what emerges, the court may exercise its power under section 81 of the Police and Criminal Evidence Act 1984 or section 20 of the Criminal Procedure and Investigations Act 1996 to exclude the expert evidence.


Statements of understanding and declarations of truth in expert reports

19B.1 The statement and declaration required by CrimPR 19.4(j), (k) should be in the following terms, or in terms substantially the same as these:


1. 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.

2. 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.

3. I know of no conflict of interest of any kind, other than any which I have disclosed in my report.

4. 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.

5. 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.

6. I have shown the sources of all information I have used.

7. I have exercised reasonable care and skill in order to be accurate and complete in preparing this report.

8. 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.

9. I have not, without forming an independent view, included or excluded anything which has been suggested to me by others including my instructing lawyers.

10. I will notify those instructing me immediately and confirm in writing if for any reason my existing report requires any correction or qualification.

11. 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.

12. I have read Part 19 of the Criminal Procedure Rules and I have complied with its requirements.

13. I confirm that I have acted in accordance with the code of practice or conduct for experts of my discipline, namely [identify the code].

14. [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 for prosecution if I have wilfully stated anything which I know to be false or that I do not believe to be true.’

Pre-hearing discussion of expert evidence

19C.1 To assist the court in the preparation of the case for trial, parties must consider, with their experts, at an early stage, whether there is likely to be any useful purpose in holding an experts’ discussion and, if so, when.  Under CrimPR 19.6 such pre-trial discussions are not compulsory unless directed by the court.  However, such a direction is listed in the magistrates’ courts Preparation for Effective Trial form and in the Crown Court Plea and Trial Preparation Hearing form as one to be given by default, and therefore the court can be expected to give such a direction in every case unless persuaded otherwise.  Those standard directions include a timetable to which the parties must adhere unless it is varied.

19C.2 The purpose of discussions between experts is to agree and narrow issues and in particular to identify:

    (a) the extent of the agreement between them;
    (b) the points of and short reasons for any disagreement;
    (c) action, if any, which may be taken to resolve any outstanding points of disagreement; and
    (d) any further material issues not raised and the extent to which these issues are agreed.

19C.3 Where the experts are to meet, that meeting conveniently may be conducted by telephone conference or live link; and experts’ meetings always should be conducted by those means where that will avoid unnecessary delay and expense.

19C.4 Where the experts are to meet, the parties must discuss and if possible agree whether an agenda is necessary, and if so attempt to agree one that helps the experts to focus on the issues which need to be discussed.  The agenda must not be in the form of leading questions or hostile in tone.  The experts may not be required to avoid reaching agreement, or to defer reaching agreement, on any matter within the experts’ competence.

19C.5 If the legal representatives do attend:

    (a) they should not normally intervene in the discussion, except to answer questions put to them by the experts or to advise on the law; and
    (b) the experts may if they so wish hold part of their discussions in the absence of the legal representatives.

19C.6 A statement must be prepared by the experts dealing with paragraphs 19C.2(a) – (d) above. Individual copies of the statements must be signed or otherwise authenticated by the experts, in manuscript or by electronic means, at the conclusion of the discussion, or as soon as practicable thereafter, and in any event within 5 business days.  Copies of the statements must be provided to the parties no later than 10 business days after signing.

19C.7 Experts must give their own opinions to assist the court and do not require the authority of the parties to sign a joint statement.  The joint statement should include a brief re-statement that the experts recognise their duties, which should be in the following terms, or in terms substantially the same as these:

    ‘We each DECLARE THAT:
    1. We individually here re-state the Expert’s Declaration contained in our respective reports that we understand our overriding duties to the court, have complied with them and will continue to do so.
    2. We have neither jointly nor individually been instructed to, nor has it been suggested that we should, avoid reaching agreement, or defer reaching agreement, on any matter within our competence.’

19C.8 If an expert significantly alters an opinion, the joint statement must include a note or addendum by that expert explaining the change of opinion.


NOTE: A previous article dealing with the 2014 revisions to the Criminal Procedure Rules can be found HERE.