What is the effect if two expert statements are almost identical?



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When representing the same party, experts should be aware of similarities in content and expression in their opinions.
Australia Litigation, Mediation & Arbitration
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Hoser v Secretary of the Department of Energy, Environment and Climate Action [2024] VSC 277

In this case, the court accorded little weight to the plaintiff's tendered expert evidence because it was apparent that much of the two statements and plaintiff's own expert opinion, in layout and expression, seemed to have been created by one person.


The plaintiff, who describes his occupation as wildlife displayer, snake catcher and scientist also keeps wildlife, mostly snakes and other reptiles. He is also a published author, including scientific papers, on reptiles.

As such, the plaintiff is licenced by the state government through the Secretary of the Department of Energy, Environment and Climate Action (the Department).

The Department visited the plaintiff 's property to inspect his wildlife. Following the visit, the plaintiff received a Direction Notice under Reg. 43(2) of the Wildlife Regulations 2013 (Vic), highlighting potential violations.

Expert Evidence

The plaintiff relied on his own expert opinion and in addition two further expert reports, appended to affidavits by Mr CW and Mr PW. This was opposed by the Secretary of the Department, based on the following reasons:

  • Neither report was before the decision maker, and the legality of a decision is generally challenged only on the material before the decision maker, save for limited exceptions.
  • The reports express irrelevant opinions and opinions beyond the expertise of the deponents, going to the merit of the decision.
  • The statements are identical or substantially similar to the plaintiff's own statements to the court, and so do not appear to be an expression of the deponent's own opinions.

The court said the plaintiff must demonstrate that a relevant exception arises to tender the affidavits, since the opinions were not presented to the decision maker (Mackenzie v Head, Transport for Victoria [2021] VSCA 100). The exceptions are: [a] if the affidavits constitute evidence capable of showing that a decision maker failed to make an obvious inquiry about a critical fact, the existence of which is easily ascertained and so is relevant to the question of whether the decision is legally unreasonable; and [b] expert evidence capable of showing that there was or was not an intelligible foundation for the decision.[30]

As to the first exception, the court accepted that the opinions of Mr CW and Mr PW could influence the assessment of whether the decision made by the Secretary's authorised delegate was legally unreasonable or lacked a clear foundation; at least as to the requirements for the welfare of reptiles and amphibians in captivity. That is, assuming that both Mr CW and Mr PW hold appropriate expertise in the keeping and husbandry of reptiles and amphibians.[31]

However, to the extent that the opinions of Mr CW and Mr PW are admissible, they are given little weight by the court. It was evident that much of the content and expression in the statements of Mr CW and Mr PW, as well as the plaintiff's own expert opinion, appear to have been created by one person. This suggested that a draft statement might have been submitted by the plaintiff for their review, rather than being independently prepared, which undermines the independence of their opinions.[32]

The court did acknowledge that each deponent has read and sworn that the contents of the affidavit are true and correct and that they hold the expressed opinions. However, it was held that beyond the specific statements made by Mr PW in paras [16] – [34] of his affidavit and Mr CW in para [27] of his affidavit, the statements have little probative value or are inadmissible as they express opinions outside their expertise. [32]

The court also observed that the usefulness of the opinions of Mr CW and Mr PW is also diminished. They primarily consist of statements or conclusory opinions that do not provide an explanation of how those opinions were derived through the application of their specialised knowledge, therefore not meeting the Makita and Dasreef requirements. [33]

More importantly, the court found that the opinions of Mr CW and Mr PW are deficient for not including reasons for reaching their conclusions. For instance, the court found Mr CW's opinion about the need for reform of the COP Reptiles is not a relevant opinion for the purpose of this proceeding and that Mr PW took the same approach, in almost identical language. The court reiterated that experts are required to set out reasons for reaching their conclusions. [34]

Key Takeaways:

  • Experts, though representing the same party, should be cautious about similarity in content and expression among their statements, which undermines their independence.
  • Experts must bear in mind the requirements of Makita and Dasreef and ensure that their opinions and conclusions are derived through specialised knowledge.

Read the full decision here.

The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.

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