Experts and expert evidence    


Evidence at a hearing may be given by witnesses (whether orally or in writing such as in an affidavit, witness statement or expert report) or in documentary form (whether documents, plans, maps or photographs). The evidence given may be of facts or opinions by experts. These pages provide information on experts giving expert evidence.

Botanist examining plants  


The general rule against opinions and the exception for expert opinions

The rules of evidence distinguish between evidence of facts and evidence of opinion. The general rule is that witnesses should only give evidence of fact, not opinion. Evidence of fact involves direct observation of facts using the five senses, such as what people saw or heard. Opinion evidence is an inference or conclusion drawn from facts. The general rule is that it is the function of the Court to draw inferences or conclusions from the facts proven by witnesses of fact. 

There is, however, an exception to the general rule for opinion evidence given by experts. Where matters involve specialised knowledge, the Court may not have that specialised knowledge so as to be able to draw the proper inferences from the facts stated by the witnesses of fact. The Court needs the assistance of a person with the specialised knowledge to be able to draw the proper inferences.

Who is an expert?

An expert is a person who has specialised knowledge based on the person’s training, study or experience.

Admissibility of expert opinion evidence

In order for expert opinion evidence to be admissible in proceedings, as an exception to the general rule against opinion evidence, it should satisfy four tests:

  • the expert opinion is to be relevant — relevant evidence is evidence that, if it were to be accepted, could rationally affect (directly or indirectly) the assessment of the probability of the existence of a fact in issue in the proceedings
  • the expert opinion is to involve specialised knowledge — the opinion of the expert must be within a field of knowledge that the law recognises as one on which expert evidence can be called
  • the witness expressing the opinion is to be qualified —  the witness must be qualified as an expert in the recognised field of knowledge and have acquired specialised knowledge based on the person’s training, study or experience
  • the expert opinion is to have a basis —  the opinion of the witness must be wholly or substantially based on the specialised knowledge and the factual basis of the opinion must be disclosed and proven by admissible evidence.

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The duties of an expert witness

Rules of Court impose duties on an expert in preparing and giving expert opinion evidence. An expert must comply with :

  • the expert witness code of conduct
  • court directions in relation to expert witnesses and their evidence
  • court directions and requirements for joint conference and report and concurrent evidence.

Expert witness code of conduct

Expert to comply with code

An expert witness must comply with the code of conduct in Schedule 7 to the Uniform Civil Procedure Rules 2005 (“UCPR”) r 31.23(1). An expert’s report and oral evidence may not be received in evidence unless the expert acknowledges that he or she has read the code of conduct and agrees to be bound by it (UCPR r 31.23(3) and (4)). 

The expert witness code of conduct imposes: 

  • a general duty to the Court
  • a duty to comply with orders
  • a duty to work co-operatively with other expert witnesses
  • requirements regarding the content of the expert’s report.

General duty to the Court

An expert witness has an overriding duty to assist the Court impartially on matters relevant to the expert witness’s area of expertise (UCPR Sch 7 cl 2(1)). An expert witness’ paramount duty is to the Court and not to any party in the proceedings (including the person retaining the expert witness (UCPR Sch 7 cl 2(2)). An expert witness is not an advocate for a party (UCPR Sch 7 cl 2(3)).

Duty to comply with Court directions

An expert witness must abide by any direction of the Court (UCPR Sch 7 cl 3).

Duty to work co-operatively with other expert witnesses

An expert witness, when complying with any direction of the Court to confer with another expert witness or to prepare a parties’ expert’s report with another expert witness in relation to any issue:

(a) must exercise his or her independent, professional judgment in relation to that issue

(b) must endeavour to reach agreement with the other expert witness on that issue

(c) must not act on any instruction or request to withhold or avoid agreement with the other expert witness (UCPR Sch 7 cl 4).

Content requirement for experts’ reports

An expert’s report must (in the body of the report or in an annexure to it) include the following:

(a) the expert’s qualifications as an expert on the issue the subject of the report

(b) the facts, and assumptions of fact, on which the opinions in the report are based (a letter of instructions may be annexed)

(c) the expert’s reasons for each opinion expressed

(d) if applicable, that a particular issue falls outside the expert’s field of expertise

(e) any literature or other materials utilised in support of the opinions

(f) any examinations, tests or other investigations on which the expert has relied, including details of the qualifications of the person who carried them out

(g) in the case of a report that is lengthy or complex, a brief summary of the report (to be located at the beginning of the report) (UCPR Sch 7 cl 5(1)).

If an expert witness who prepares an expert’s report believes that it may be incomplete or inaccurate without some qualification, the qualification must be stated in the report (UCPR Sch 7 cl 5(2)). If an expert witness considers that his or her opinion is not a concluded opinion because of insufficient research or insufficient data or for any other reason, this must be stated when the opinion is expressed (UCPR Sch 7 cl 5(3)).

If an expert witness changes his or her opinion on a material matter after providing an expert’s report to the party engaging him or her (or that party’s legal representative), the expert witness must forthwith provide the engaging party (or that party’s legal representative) with a supplementary report to that effect (UCPR Sch 7 cl 5(4)).

An expert witness must disclose in his or her expert’s report any arrangements under which the charging of fees or costs by the expert witness is contingent on the outcome of the proceedings or the payment of any fees or costs to the expert is to be deferred (UCPR r 31.22(1)). The Court may direct disclosure of the terms of the expert witness’s engagement (UCPR r 31.22(2)).

Court control over giving of expert evidence

Court rules emphasise that the Court retains control over the giving of expert evidence (eg UCPR r 31.17(a) ). This is necessary to ensure integrity of the evidence, proportionality and the just, quick and cheap resolution of the real issues in proceedings.

Court directions regarding expert witnesses

The Court may at any time give such directions as it considers appropriate in relation to the use of expert evidence in proceedings (UCPR r 31.20(1)). Directions may include:

(a) a direction as to the time for service of experts’ reports;

(b) a direction that expert evidence may not be adduced on a specified issue;

(c) a direction that expert evidence may not be adduced on a specified issue except by leave of the Court

(d) a direction that expert evidence may be adduced on specified issues only

(e) a direction limiting the number of expert witnesses who may be called to give evidence on a specified issue

(f) a direction providing for the engagement and instruction of a parties’ single expert in relation to a specified issue

(g) a direction providing for the appointment and instruction of a Court-appointed expert in relation to a specified issue

(h) a direction requiring experts in relation to the same issue to confer, either before or after preparing experts’ reports in relation to a specified issue

(i) any other direction that may assist an expert in the exercise of the expert’s functions

(j) a direction that an expert who has prepared more than one expert’s report in relation to any proceedings is to prepare a single report that reflects his or her evidence in chief.

Joint conferencing of experts

The Court may direct expert witnesses:

(a) to confer, either generally or in relation to specified matters

(b) to endeavour to reach agreement on any matters in issue

(c) to prepare a joint report, specifying matters agreed and matters not agreed and reasons for any disagreement

(d) to base any joint report on specified facts or assumptions of fact, and may do so at any time, whether before or after the expert witnesses have furnished their experts’ reports (UCPR r 31.24(1)).

The Court may direct that a conference be held:

(a) with or without the attendance of the parties affected or their legal representatives

(b) with or without the attendance of the parties affected or their legal representatives, at the option of the parties

(c) with or without the attendance of a facilitator (that is, a person who is independent of the parties and who may or may not be an expert in relation to the matters in issue) (UCPR r 31.24(2)).

Experts may apply to the Court for directions

An expert witness so directed may apply to the Court for further directions to assist the expert witness in the performance of his or her functions in any respect (UCPR r 31.24(3)). Application must be made by sending a written request for directions to the Court, specifying the matter in relation to which directions are sought (UCPR r 31.24(4)). An expert witness who makes such an application must send a copy of the request to the other expert witnesses and to the parties affected (UCPR r 31.24(5)).

Joint report of experts

The joint report is to specify matters agreed and matters not agreed and the reasons for any disagreement (UCPR r 31.26(2)). The joint report may be tendered at the trial as evidence of any matters agreed (UCPR r 31.26(3)). In relation to any matters not agreed, the joint report may be used or tendered at the trial only in accordance with the rules of evidence and the practices of the Court (UCPR r 31.26(4)). Except by leave of the Court, a party affected may not adduce evidence from any other expert witness on the issues dealt with in the joint report (UCPR r 31.26(5)).

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Means of receiving expert evidence

The Court may receive expert evidence by various means: 

  • parties may engage their own individual experts to give evidence in Court

  • parties may agree to appoint a single expert who will give evidence in Court

  • the Court may appoint an expert to assist the Court in various ways, including by giving evidence in Court.

For hearings in Classes 1, 2 and 3 of the Court’s jurisdiction, the rules of evidence do not apply and the Court may inform itself of any matters in such manner as it thinks appropriate and as the proper consideration of the matters before the Court permit: s 38(2) of the Act. This enables Commissioners with special knowledge, experience and qualifications in particular fields of knowledge, to use that knowledge and experience in understanding and determining issues concerning those fields of knowledge raised in the proceedings. Any such use, however, must conform to the rules of procedural fairness, including disclosure to the parties and providing an opportunity for the parties to be heard, such as by adducing evidence and making submissions, on the matters disclosed by the Commissioner.

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How is expert evidence given at the hearing?

On-site hearings

Some types of proceedings can be heard on the site of the dispute. For on-site hearings, all evidence including expert evidence is generally presented on-site. 

When site inspections are conducted as part of conciliation conferences or Court hearings, experts who have prepared evidence for the proceedings should ensure that they are available to attend the site inspection. Experts should ensure that any aids they require to support their evidence, such as height poles, or the pegging out of any proposed buildings, are in place at the time of the site inspection or hearing. Experts should also ensure that access to relevant properties is available on the site inspection. Experts may be called upon by the Court to explain their evidence on site so a greater understanding of their evidence is available when the hearing resumes in Court.

Individual expert evidence

Experts may be called individually to give evidence in a Court hearing. When entering the witness box, an expert should bring all necessary information, including any expert reports or background information relied on by the expert in the preparation of his or her evidence, to assist the expert in giving evidence.   

The expert may be asked questions about his or her evidence by the party calling the witness or the party’s legal representative (examination in chief) and then by the opposing party or legal representative (cross-examination).

Individual expert evidence is used less frequently in appeals in Classes 1, 2 and 3 of the Court’s jurisdiction where concurrent evidence is more common.

Concurrent evidence

The Court may direct that the evidence of the expert witnesses be given concurrently (UCPR r 31.35). Experts, grouped in disciplines, are sworn in together and sit next to each other in the witness box or bar table or other convenient location visible to the parties and the Court. The presiding judge or Commissioner takes an active role in the process, acting as a chair of the discussion.


An agenda for oral evidence is settled. Usually the issues disagreed in the joint report form the basis for the agenda. The Court gives directions as to the manner in which the evidence is to be given (UCPR 31.35). Usually each expert in turn is given an opportunity to explain their opinion on each issue and give their opinion about the opinion of another expert witness. There may be a dialogue in the form of a structured, orderly debate. Experts may ask questions of each other. At the conclusion of this dialogue, the Court may ask questions. Parties are then given an opportunity to examine the experts. This may involve examination in chief and cross-examination.

Concurrent evidence is the usual way in which the expert evidence of the parties’ experts is given at a Court hearing of proceedings in Classes 1, 2 and 3 of the Court’s jurisdiction. The benefit of this approach is that it facilitates a discussion between the experts, the advocates and the Judge or Commissioner and helps to narrow the issues in dispute.

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