Every litigator who briefs experts has had the experience of opening a draft report and feeling a quiet drop in the stomach. The opinion is fine but the reasoning is gone. Or the assumptions are wrong. Or the witness has wandered into a paragraph that no person in their field could give.
Thankfully, there is ample case law on expert evidence across the NSW courts, the Federal Court, and the family law courts to see what judges actually write when this happens. The themes are consistent across jurisdictions. The fixes are mostly on our side of the desk.
The expert is not your advocate
The clearest cluster of judicial criticism concerns experts who have, consciously or otherwise, slipped into the role of advocate. Sometimes the language is gentle. Often it is not.
“The provocative language contained throughout the Watts report, especially in Section 3, together with the unsupported and unprofessional allegations made against KPMG and the KPMG report, strongly suggest, however, that Mr Watts has crossed over the rubicon from objective and impartial expert witness to partisan advocate for UTSG.”UTSG Pty Ltd v Sydney Metro (No 4) [2019] NSWLEC 51 at [46]
The same complaint appears in patent litigation in the Federal Court (Rofe J in Boehringer Ingelheim Animal Health USA Inc v Zoetis Services LLC [2023] FCA 1119 at [264], where the expert understood his duty to be to his client first and the Court second), in earlier Federal Court matters (Jacobson J in Synthetic Turf Development Pty Limited v Sports Technology International Pty Limited [2005] FCA 69 at [234]: “a most unsatisfactory expert witness… an advocate for the cause propounded by the applicant rather than an independent expert”), and in the family law courts (Sigley & De Santis (No. 3) [2020] FamCA 883 at [16]: “Mr C was not independent and he acted as an advocate rather than as an expert”). Signing the Code is no protection. Judges look at how the report reads and how the witness behaves in the box. What tips a witness into the advocate’s chair is most often tone (provocative language, characterisations of the other side, refusal to make concessions) rather than the substantive opinion. That is correctable at the draft stage if we read drafts with that lens.
The reasoning has to be on the page, not in the witness box
Twenty-five years after Heydon JA’s judgment in Makita (Australia) Pty Ltd v Sprowles (2001) 52 NSWLR 705; [2001] NSWCA 305, the same problem keeps reaching judgment. An expert states a conclusion. The reasoning that supports it does not appear in the report. The witness then tries to repair this in cross-examination. The cost is borne by the party who tendered the expert. In Miljus v CSR Ltd (No. 2) [2010] NSWSC 598 at [19], Davies J recorded that material analysis given for the first time in the witness box put the other side at “great disadvantage” and forced an adjournment for a responsive report. The Land and Environment Court has put the principle bluntly in Secretary, Department of Planning and Environment v Leda Manorstead Pty Ltd (No 6) [2020] NSWLEC 68 at [30]:
“A bare ipse dixit (or, ‘I say so’) will not suffice and is likely to render an expert report inadmissible on the basis that it will neither be intelligible and convincing nor capable of testing.”Leda Manorstead (No 6) [2020] NSWLEC 68 at [30]
The Federal Court treats reasoning that surfaces only in the witness box as a weight problem rather than a strict admissibility problem, but the consequence is the same. In Sun Pharma ANZ Pty Ltd v Otsuka Pharmaceutical Co Ltd [2025] FCA 44 at [75], Downes J recorded that an expert had performed Excel calculations that were “not contained in his affidavits, or referred to by him as forming part of his reasons for his conclusions, contrary to clauses 3(d) and 3(e) of the Harmonised Expert Witness Code of Conduct”, and that this affected the weight to be attached to that opinion evidence.
Bad instructions produce bad reports
This is the part of the case law most directly within the lawyer’s control. The judgments say plainly that the quality of the report tracks the quality of the brief: see Ryder v Frohlich [2006] NSWSC 833 at [37] (“If those instructions are incorrect or are misleading the assumptions upon which an expert report is based will be incorrect and so will be the expert’s conclusion”). The same point was made more pointedly by Payne J in KinCare Community Services Limited v Chief Commissioner of State Revenue [2019] NSWSC 182 at [56]:
“This case was made much more difficult by the Commissioner’s expert embarking on the task of reconstructing KinCare’s audited financial statements without any assumptions of fact being identified or guidance being given about how to approach the task.”KinCare [2019] NSWSC 182 at [56]
Every factual assumption in the report needs to be sourced to a witness statement, a tendered document, or admitted evidence. If it cannot be sourced at the briefing stage it will not be in evidence later, and the opinion built on it will be discounted accordingly: see Lloyd v Thornbury [2019] NSWCA 154 at [153] (Gleeson JA, Meagher JA agreeing). The Commissioner did not lose KinCare because of the expert. The Commissioner lost time and credibility because of the brief. That is a problem the lawyer can fix at the start.
The New Aim v Leung saga
The recent Federal Court decisions in New Aim v Leung are widely cited as the leading “lawyer drafted my expert report” example. The story runs across three judgments, and the practical lessons sit underneath the headline reversal on appeal.
The trial
The underlying case was a claim by New Aim against a former employee and two competitors for breach of confidence, breach of contract, and contravention of s 183 of the Corporations Act 2001: New Aim Pty Ltd v Leung [2022] FCA 722. New Aim engaged Ms Fangyun (Lindy) Chen of ChinaDirect Sourcing as its independent expert through Corrs Chambers Westgarth. The chronology was extracted from Ms Chen at trial only after counsel called for production of her laptop. Corrs sent Ms Chen an engagement letter on 21 February 2022. The next day Ms Chen sent Corrs her “Bio”, a “Script about ChinaDirect Sourcing”, and a sample inspection report. On 25 February a Corrs lawyer emailed her: “we are progressing your witness statement and would like to arrange a call with you next week to discuss it further”. A video conference followed on 2 March. The letter of instruction was signed by the Corrs partner on 7 March, and that evening Corrs emailed: “We will send to you your draft statement shortly”. The draft witness statement and expert report arrived at 11:40am the following morning. Ms Chen signed and filed it the same day.
McElwaine J rejected Ms Chen’s evidence in its entirety. He found that “most of the report was, at least initially, the product of drafting by the lawyers for the applicant” (at [158]) and that “the conduct engaged in preparing and delivering the report of Ms Chen was misleading” (at [163]). The letter of instruction of 7 March had represented that Ms Chen was being asked to “prospectively consider” two questions, but Corrs already had a draft in train by 25 February. New Aim’s claims were dismissed.
The appeal
The matter went to a five-judge bench (Kenny, Moshinsky, Banks-Smith, Thawley, and Cheeseman JJ) because of a possible question over Futuretronics: New Aim Pty Ltd v Leung [2023] FCAFC 67. The Full Court unanimously held that the primary judge had erred in rejecting the entirety of Ms Chen’s evidence.
“There is not one rule or practice which covers all experts or all situations. For example, in the typical case where medical opinion evidence is required, the medical expert would ordinarily draft his or her own report. The same is generally true of an expert valuer preparing a valuation or an accountant preparing a report about economic loss… Nevertheless, a number of situations might arise where legal practitioners are involved [in drafting]…”New Aim v Leung [2023] FCAFC 67 at [314]
“The primary judge observed at [76] that, if legal practitioners are involved in the drafting of an expert report that fact must be disclosed in the expert report. This may well be desirable, forensically or otherwise, but there is no legal obligation as such to do so. Whether there is an ethical obligation to do so depends on the particular circumstances.”New Aim v Leung [2023] FCAFC 67 at [315]
The Full Court drew a distinction between paragraphs 1 to 55 of Ms Chen’s report (factual material about her own business, drafted by Corrs from the Bio and Script she had provided) and paragraphs 56 to 60 (the actual opinion). The factual drafting was held to be “unremarkable” (at [293]). The appeal was allowed and the proceeding remitted for retrial. In New Aim Pty Ltd v Leung (No 3) [2023] FCA 1295, O’Callaghan J held that the order was for a new trial under s 28(1)(f) of the Federal Court of Australia Act 1976 rather than a continuation under s 28(1)(c).
What this saga teaches
The proposition that lawyers cannot help draft expert reports was tested at first instance and reversed on appeal. That is not the law in the Federal Court. The more useful lessons sit underneath. What turned the trial judge was the choreography, not the drafting: a letter of instruction dated 7 March, when a draft already existed by 25 February, looks contrived on any reading. Date the brief at the point it is actually given. The opinion section of any expert report (whichever paragraphs that is) is the part the expert must own and visibly own. A drafting trail showing the expert sending opinion text to the lawyers, rather than receiving it from them, prevents the problem. Finally, reputational cost survives reversal: Ms Chen’s name is now permanently associated with a widely-reported first-instance judgment that was not corrected for almost a year.
A short checklist before you send the brief
The assumed facts the expert must take as given should be set out in the brief, and each one should be sourced to a document, witness statement, or admission that will prove it at trial.The questions should be framed inside the expert's specific sub-specialty. If a question reaches into another field, brief a second expert in the second field rather than letting the first expert reach.Tell the expert that conclusions without a chain of reasoning will be cut from the report. Quote Makita at them if needed.Read drafts for tone. Provocative language, characterisations of the other side, and unprofessional allegations are the markers that turn an expert into an advocate.Re-read the Code with the expert at the briefing stage rather than the morning of the hearing. The relevant text is UCPR Schedule 7 in NSW, the Harmonised Expert Witness Code annexed to GPN-EXPT in the Federal Court, or NCAT Procedural Direction 3.In family law, treat the letter of instruction as the work product. The single expert's report will reflect the questions asked.Plan the joint conclave from the outset. The questions in the conclave letter will determine which opinions survive. Draft them as if they will be read aloud.Jake McKinley notes that this article is written for the purpose of providing generalised information and not to provide specialised legal advice. If you require qualified legal advice on anything mentioned in this article, our experienced team of solicitors at Jake McKinley are here to help. Please get in touch with us on 02 9232 8033 today to make an enquiry.
Article Written by Jacob Carswell-Doherty, Principal
