Tips on expert opinion evidence

Expert opinion evidence plays a central role in much litigation. In this article, we outline 10 tips that solicitors should keep in mind, when they’re briefing and working with an expert who will be called to give evidence.

Consider whether you can, and should, brief an expert

Expert opinion evidence is a recognised exception to the general prohibition against opinion evidence. However, it will only be possible to admit such evidence where the application of specialised knowledge is needed in order for sound inferences to be drawn, or conclusions reached. As Heydon J commented in Dasreef Pty Ltd v Hawchar [2011] HCA 21, [90] expert opinion evidence:

“is a bridge between data in the form of primary evidence and a conclusion which cannot be reached without the application of expertise.”

A key question before deciding to brief an expert is: are there any issues arising, or likely to arise, for which a conclusion cannot be reached without the application of expertise? Ask yourself, would an ordinary person be able to form a sound judgment based on their common experience, or is assistance from a witness possessing specialised knowledge actually required?

One example in which an expert’s opinion was rejected by a Court was in Honeysett v The Queen [2014] HCA 29.

In that case, the High Court considered evidence from Professor Henneberg in relation to the identification of a burglar whose head had been obscured from vision in CCTV footage. Professor Henneberg was an expert in anatomy, and he gave evidence that anatomical characteristics of the person seen in the footage matched those of the accused.


However, the High Court said that the identification made by Professor Henneberg was based on his “subjective impression of what he saw when he looked at the images”, and this was not a subject on which an expert’s views were required.

Assuming the case is one in which expertise is required, the next question is whether you should obtain an expert opinion. In this regard, apart from the cost and time involved, key considerations will include:

  • is the evidence relevant to a matter in issue? Remember, the matters in dispute are defined by the pleadings. A civil proceeding is not a Royal Commission trying to turn every stone or ‘get to the bottom of things’. 
  • will obtaining the evidence be consistent with the overriding obligation under rule 5 of the Uniform Civil Procedure Rules, of facilitating the just and expeditious resolution of the real issues at a minimum of expense? If the expense and time required of the parties by the evidence is grossly disproportionate to what is in issue, then perhaps not.
  • is it actually likely to help your client? A report may be relevant and admissible but still not strategically desirable. That might be the case where your opponent bears the onus of proving some particular matter. If an expert report might help build a case for your opponent, it may be better not to obtain it. 

If in doubt, it’s usually better to lean on the side of obtaining an expert report. Failure to do so, where expertise is required, may result in you failing to prove your case. If the report is not necessary, ordinarily the worst that can happen is that it simply won’t be admitted. 

Be careful who you choose

Having decided to seek an expert’s opinion, who should you retain? There are some must haves, and some good to haves.

The must haves are that the person is, by reason of training, study or experience, an expert in a field of specialised knowledge. Keep in mind that it is not always straight forward to work out who actually is an expert, particularly in new and emerging fields (for example, cryptocurrency).

Make sure you clearly explain the issues in relation to which an opinion is sought, have the expert confirm, and satisfy yourself, that those issues actually fall within their area of expertise.


The ‘good to haves’ are more diverse, but you might want to consider the following:

  • after an initial discussion, do they appear to have a good grasp of the issues? Can they express themselves clearly when speaking?
  • can you review examples of their published writings, including any expert reports they’ve previously written? Again, can they express themselves clearly in writing, in a way that will lend credibility to any report they produce?
  • do they seem like they’ll be easy enough to work with? Are they tempered, reasonable? Do they inspire confidence, or not? Keep in mind that they may be cross-examined – and their credit affected accordingly.
  • can they meet the timelines you need them to, having regard to any court deadlines? Keep in mind that you’ll need time to form a view on whether any additional reports or investigations are required.
  • have they had any experience as an expert witness? Some experience will likely be helpful; but be sure to review what the published judgments say about the value or otherwise of their evidence.

Brief well and brief early

It’s part of your role to make sure that the expert understands theirs. That includes what is expected of their report. The expert may be an expert in biology, chemistry, engineering or what have you – but they are almost certainly not an expert in producing a compliant and admissible report.

Make sure you inform the expert of:

  • the requirements provided for by Chapter 11, Part 5 of the Uniform Civil Procedure Rules – particularly the requirements for a report provided by rule 429H; 
  • the common law requirements, outlined by Heydon JA in Makita (Australia) Pty Ltd v Sprowles [2011] NSWCA 305 (particularly at [85]). This includes the all-important requirement that the expert identify the assumptions or basis of any opinions they express, and “furnish the trier of fact with criteria enabling evaluation of the validity of the expert’s conclusions” (at [59]);
  • the desirability of their report being comprehensible to a lay reader, free from unnecessary jargon and acronyms, and structured and presented in a way that will enhance its readability; and
  • about other aspects of their role, including the requirement that they not ‘swear the issue’ by wading into the ultimate legal questions in dispute, and about their obligations under the Code of Conduct (in Schedule 1C of the UCPR) – a copy of which you must provide them.

Part of your brief to the expert will include the issues on which you seek their opinion. As Justice Dalton (as her Honour then was) said in Landel Pty Ltd v Insurance Australia Ltd [2021] QSC 247, [34]:

“It is the job of the lawyers in any case to define questions upon which they seek expert opinion. This has to be carefully done so that the expert opinion obtained is relevant to the legal issues in the case.”

Ideally you will have discussed with the expert (or another ‘shadow’ expert) the appropriate questions to ask before formalising them, to ensure that they are indeed the real and relevant questions to ask, are framed correctly, and seek only opinions within the expert’s expertise.


Take particular care when instructing the expert to assume any facts for the purposes of their report. Will those assumptions align with what you can, and will, be able to prove at trial? Nothing will reduce the value of an expert’s opinion more than a misapprehension by them about the relevant facts on which they base their opinion. If the facts change, make sure the expert is updated as soon as possible.

Be careful what is put in writing

It’s safest to proceed on the assumption that anything that you, or the expert, put in writing, may come into the hands of your opponent, and be used for the purposes of cross-examination.

There are many ways that documents may end up in the hands of another party. One circumstance is where the documents are not privileged in the first place; another may be where privilege is waived.

To minimise these risks, think carefully before you reduce anything to writing, and instead of shooting off an email, consider picking up the phone. Engaging orally with experts, at least initially, is a well-accepted practice. As Justice Dalton (as her Honour then was) observed in Landel Pty Ltd v Insurance Australia Ltd [2021] QSC 247, [25]: “I see no difficulty with an initial oral retainer, or indeed an initial oral exchange of views prior to the engagement of an expert.”

In the same judgment, her Honour noted that, at [28]:

“since changes to disclosure rules to make expert opinion disclosable there has been a practice of orally engaging experts and receiving, at least their initial, opinions orally. Only if the expert’s initial oral opinion is favourable are documents produced. To my understanding this is a common practice and permitted by the rules.”


Inform the expert that their documents will ordinarily be discoverable, or may be the subject of a subpoena, and likely used in cross-examination. Further, invite them to pick up the phone to you, should the need arise.

The greatest prospect of preserving the confidentiality of any discussions had with an expert, for instance as to any preliminary views, may be to remember the substance of any such discussion and put it in an advice to the client.1 But remember that a Court can look behind any claim of privilege, and a judge won’t be impressed – and is unlikely to uphold a claim of privilege – if a so-called ‘advice’ is little more than a compendium of file-noted conservations.

In relation to the viewing of draft reports, an article by Richard Douglas KC suggests that it is in vogue for “a draft report to be viewed under an expert controlled platform”.2 That may mean that it is not in the ‘possession or control’ of a party for the purposes of the disclosure rules (UCPR r 211). However, that won’t prevent the possibility that the document/s become available because of a subpoena to the expert. And it doesn’t preclude the potential for embarrassment should such an approach come to light in cross-examination.  

Conference with your expert/s

Conferencing with your experts helps them prepare to give their evidence, and helps you ensure that you make the most of their knowledge in preparation for any trial.

When it comes to giving evidence in court, ordinarily your expert will be a ‘fish out of water’. As Justice Henry has observed:3

“They will be less apprehensive, better functioning witnesses if they have been informed in advance about matters of process, refreshing memory before testifying, the notion of only answering the question asked of them, the process of cross-examination, re-examination and the like.”


However, remember that, as with other witnesses, you must not conference with expert witnesses together, lest their independence be undermined. The whole notion of experts ‘hot-tubbing’ in the witness box might indicate a relaxation of this requirement in relation to experts, that’s not the case. In your dealings with them, experts should generally be kept apart.

In Landel Pty Ltd v Insurance Australia Ltd [2021] QSC 247, Justice Dalton observed (at [26]) that she was:

“…critical of the defendant’s lawyers for meeting with both experts together. … Here, where the plan apparently was to present two independent views to the Court, meeting with both experts together, particularly before they had committed their views to writing, obviously had the potential to compromise that independence.”

Experts are a tremendous resource, and you should use the opportunity to squeeze all the knowledge out of them you can. That may help you, and your counsel, formulate meaningful and incisive questions to ask your opponent’s witnesses in cross-examination, and put you in a better position to identify weaknesses in your opponent’s case.

Should you consider squeezing some knowledge out of your opponent’s experts too? As Justice Henry observes in a paper from 2016, the rule that there is no property in a witness applies equally to expert witnesses. His Honour said:4

“The advantage likely to accrue to a potential cross-examiner in conferring in advance of a trial with an opponent’s expert is self-evident. Surprisingly, at least in my time at the Bar, it was very rare for my side’s expert to have been contacted by the other side’s lawyers with a view to them conferring with the witness.”


His Honour also observed that, in his experience, experts seemed “more willing than lay witnesses to participate in conferences with lawyers acting for opposing sides”, perhaps because they “pride themselves on appearing objective”.

Of course, keep in mind that, if you approach your opponent’s experts, your opponent may be more likely to consider approaching yours too!

Part two tomorrow

1 Richard Douglas KC, ‘Expert evidence in civil litigation – formulation and management’ (2022, Hearsay) <>.
2 Ibid
3 Justice Henry, ‘Expert Evidence: A view from the bench’ (2016, speech to the Australian Lawyers Alliance National Conference).

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