Recently, the New Zealand Law Society Te Kāhui Ture o Aotearoa has received queries about whether it is permissible for counsel to ask an expert witness to amend or remove material from a court report, for the benefit of their client. This article provides guidance on this issue and examines counsels’ professional obligations when interacting with expert witnesses.¹

The starting point is always the unique position of an expert witness. In the civil context, an expert witness is bound by the Code of Conduct of Expert Witnesses in the High Court Rules 2016. The Court has held that the relevant obligations do not differ in the criminal context and apply to expert witnessess in criminal trials.²

The special role expert witnesses play in assisting the decision-maker is reflected in the statutory provisions dealing with admissibility “…[an expert opinion] is admissible if the fact-finder is likely to obtain substantial help from the opinion in understanding other evidence in the proceeding or ascertaining any fact that is of consequence to the determination of the proceeding.”³

Consonant with this unique role, key obligations for all expert witnesses are that:

• An expert witness has an overriding duty to assist the court impartially on relevant matters within the expert’s area of expertise.
• An expert witness is not an advocate for the party who engages the witness (emphasis added).

The role of expert witness is to provide impartial, independent assistance to the Court. As a corollary to that, lawyers have specific obligations to take reasonable steps to ensure that the expert’s independence is preserved.⁴ As some commenters have described it, the expert witness should not be considered part of counsels’ “legal team”.⁵

Lawyers’ obligations to uphold the special role of expert witness, aligns with counsels’ broader duty of fidelity to the Court:

• r.13.1 “A lawyer has an absolute duty of honesty to the court and must not mislead or deceive the court.”

As will be self-evident from this context, counsel engaging an expert witness needs to exercise caution in the way they interact with and make any requests of an expert witness. The primary concern is always to avoid any perception that the lawyer seeks to undermine the independence of the expert witness or compromise their overriding duty to the Court.

What does this mean in practice for counsel – how far can a lawyer go in engaging with an expert witness on their client’s behalf?

• A lawyer can and should discuss with the expert witness the content of their evidence to test whether and how it addresses the key issue(s) or questions before the Court.
• Counsel can assist the expert witness, for example, through asking pertinent questions to point out gaps or inconsistencies in the expert’s evidence or other witness evidence for the expert to consider. Counsel can also address potential weaknesses with the expert witness – for example, raising areas where the expert witness may need to consider clarifying or expanding on a statement. Counsel can and should also point out irrelevant material or issues around the admissibility of proposed evidence.⁶
• The lawyer must also ensure the expert witness is properly briefed and has all the relevant information before them.

Editing or re-framing expert witness briefs should be approached very cautiously to avoid the perception that the lawyer is ‘shaping’ the experts’ evidence thereby undermining neutrality. ⁷

In relation to the question of whether it is permissible for counsel in advocating for their client’s position to ask an expert to remove or amend their report, the answer from Lord Denning on this point is clear:

“... [counsel] must not ask a medical expert to change his report, at their own instance, so as to favour their own legally-aided client or conceal things that may be against him. They must not ‘settle’ the evidence of the medical experts as they did in Whitehouse v Jordan, which received the condemnation of this court (see [1980] 1 All ER 650 at 655) and the House of Lords. As Lord Wilberforce said ([1981] 1 All ER 267 at 276, [1981] 1 WLR 246 at 256–257):

‘Expert evidence presented to the court should be, and should be seen to be, the independent product of the expert, uninfluenced as to form or content by the exigencies of litigation.’”⁸

The position in New Zealand remains aligned with that taken by Lord Denning. The advocate “should in no way shape or coach the expert’s evidence” to fit their theory of the case or advance their client’s position.⁹ More pointedly, commentators are clear that “A lawyer should never suggest that an expert witness's report be altered or modified to remove unfavourable aspects. Such conduct is usurping the fact-finding responsibilities of the Judge or jury.”¹⁰ Ultimately, a lawyer can decline to call an expert witness who will not support the client’s case.

What are the consequences of a failure to adhere to the principles of expert neutrality?

The impact can be significant not only in terms of the proceedings themselves, but also professionally for both the expert witness and counsel, including that:

• Section 26 (2) of the Evidence Act permits the Court to exclude evidence of an expert witness who has not complied with the applicable rules of Court. Even if the evidence is not excluded:
  • the evidence may be given less weight
  • the reliability or credibility of the expert witness's evidence may be called in to question
  • another expert witness's evidence may be preferred.
• Attempting to influence or make inappropriate requests of an expert witness could also be a complaints and disciplinary matter for the lawyer involved. The rules in Chapter 13¹¹ are clear that a lawyer must not mislead or deceive the Court. The authors of Professional Responsibility in New Zealand observe that the “correct dealing with witnesses is fundamental to the integrity of the court and justice system”.¹² Respecting and preserving the independence of expert witnesses is an integral part of this.
• The reputation of the professional expert witness is also on the line when they present evidence. Any suggestion that an expert witness has been improperly influenced or lacks impartiality can have a negative impact on their reputation and could result in disciplinary action in their own regulated sphere. An expert’s willingness to work with particular counsel in the future could also be undermined if there is a perception that the lawyer may seek to shape or influence expert witness evidence.
• As with all professional obligations, if in doubt, seek advice or guidance from a trusted senior colleague or the Law Society’s Panel of Friends. 

1. For broader discussion of expert witness obligations see: CLE New Zealand Law Society seminar ‘Expert Witnesses – important issues’, Chris Browne and Julie-Anne Kincade, May 2025 available at lawyerseducation.co.nz and Matthew Palmer (ed) Professional Responsibility in New Zealand (online looseleaf ed, LexisNexis)

2. HCR Code of Conduct of Expert Witnesses and see: R v Hutton [2008] NZCA 126 and R v Carter (2005) 22 CRNZ 476

3. S25(1) Evidence Act 2006

4. r13.10.9 Lawyers and Conveyancers (Lawyers: Conduct and Client Care) Rules 2008

5. See: Professional Responsibility in New Zealand at 25.8

6. See Professional Responsibility in New Zealand at 25.2 fn 25

7. See discussion by J Kincade KC and C Browne (fn 1 above), at 21 which includes reference to the cautionary case of Hudspeth v Scholastic Cleaning and Consultancy Service Pty Ltd [2014] VSCA 78

8. Kelly v London Transport Executive [1982] 2 All ER 842 at 851 per Lord Denning (CA); Whitehouse v Jordan [1981] 1 All ER 276

9. Professional Responsibility in New Zealand at 25.8

10. See: Professional Responsibility in New Zealand at 25.3

11. Lawyers and Conveyancers Act ( Lawyers: Conduct and Client Care) Rules 2008

12. Professional Responsibility in New Zealand at 25.2