January 13, 2025
According to the rule against opinion evidence, witnesses are not ordinarily permitted to express opinions on matters. However, expert (opinion) evidence is a recognised exception to this rule, where specialised knowledge is required to draw inferences and conclusions. In this three-part series, we will explore the nature of expert opinion evidence, considerations when finding the ‘right’ expert and who their duty is to, as well as the conclaving process and joint expert reports.
WHAT IS EXPERT OPINION EVIDENCE?
Expert evidence is provided by those duly qualified to express some opinion in a particular area of expertise, where the expert’s opinion is a reasoned conclusion drawn from specialised knowledge based on facts which the expert has observed, assumed, or been instructed to assume. As Heydon J stated in Dasreef, 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”.[1]
Examples of expert witnesses may include medical pathologists, criminologists, engineers or building code specialists. Regardless of the particular field of expertise, an expert witness will only be required when certain facts need to be assessed and understood in their specialist (usually scientific) context. Furthermore, an expert witness may be called to give opinion evidence in court proceedings or in alternative dispute resolution procedures (e.g., mediation or arbitration).
PURPOSE & SIGNIFICANCE OF EXPERT OPINION EVIDENCE
Because proceedings typically relate to complex subject matters, expert evidence is invaluable for courts to receive the benefit of objective and impartial assessment of an issue from a witness with specialised knowledge. Indeed, whole categories of cases may be dominated by issues that can only be resolved with expert knowledge. As technology and science advances, it is becoming increasingly possible for courts to establish the truth or otherwise of certain allegations by technical processes, so courts have more need of experts to explain to them what they have done, why they have done it, and what conclusions they draw from their investigations.
In construction law, expert evidence is particularly important. Projects are often quite complex, with disagreements over delays, defects, or costs which can quickly spiral into courtroom battles. As such, experts are crucial in navigating technical details in order to assist with reaching a fair and objective resolution.
ADMISSIBILITY OF EXPERT OPINION EVIDENCE
In the law of evidence, ‘admissibility’ broadly refers to the principles determining whether or not particular items of evidence may be received by the court. As the High Court established in Clarke v Ryan,[2] three conditions must be met for expert opinions to be admissible:
1. The subject on which the opinion will be given is something on which the court needs the help of a third party, as opposed to relying upon its general knowledge and common sense (common knowledge rule);
2. The claimed knowledge or expertise should be recognised as credible by others who are capable of evaluating its theoretical and experiential foundations (field of expertise rule); and
3. The witness must have sufficient knowledge and experience to entitle him or her to be held out as an expert who can assist the court (expertise rule).
Common Knowledge Rule
The common knowledge rule posits that the opinion of witnesses possessing peculiar skill is admissible whenever the subject-matter of inquiry is such that inexperienced persons are unlikely to prove capable of forming a correct judgment upon it without such assistance.[3] As such, decision makers must consider when a fact becomes such common knowledge that it no longer requires an expert witness to testify as to its fundamental truthfulness.
Field of Expertise Rule
According to the field of expertise rule, the opinion must form part of the body of knowledge or experience which is sufficiently organised or recognised to be accepted as a reliable body of knowledge or experience.[4] In other words, a purported expert cannot give evidence in relation to areas of knowledge that do not form part of a ‘formal sphere of knowledge’.
Expertise Rule
Finally, the expertise rule asserts that the expert witness must be qualified by training or practical experience in an area of knowledge beyond that possessed by the trier of fact.[5] This means that an ‘ad hoc’ expert, who despite having no formal training or qualifications in a particular area of expertise but has acquired expertise based on particular experience in an area, is still deemed to have satisfied this rule.[6]
Stay tuned for next week’s instalment, where we will examine the duties and responsibilities of expert witnesses, and things to consider when finding the ‘right’ expert.
Lamont Project & Construction Lawyers
The Lamont Project & Construction Lawyers team has extensive knowledge and experience dealing with expert evidence. With this knowledge and expertise, Lamont Project & Construction Lawyers can provide the required support and advice for disputes of all scopes and sizes.
If you would like to discuss any matters raised in this article as it relates to your specific circumstances, please contact Lamont Project & Construction Lawyers.
The content of this article is for information purposes only and does not discuss every important topic or matter of law, and it is not to be relied upon as legal advice. Specialist advice should be sought regarding your specific circumstances.
Contact: Peter Lamont or Cliff Mei
Email: [email protected] or [email protected]
Phone: (07) 3248 8500
Address: Level 2, 349 Coronation Drive, Milton Qld 4064
Postal Address: PO Box 1133, Milton Qld 4064
[1] Dasreef Pty Ltd v Hawchar [2011] HCA 21, [90].
[2] 103 CLR 486, [106] (Dixon CJ) (‘Clarke’).
[3] Ibid, [106].
[4] Christie v The Queen [2005] WASCA 55, [79].
[5] Clarke (n 3).
[6] R v Butera (1987) 164 CLR 180.