Expert Witness Duties in Residential Construction Disputes (Australia)

What it is

An expert witness is a person with specialised knowledge whose opinion the court or tribunal admits as evidence. In a residential building dispute the expert is usually a building consultant, structural engineer, hydraulic engineer or quantity surveyor. The expert's job is to help the decision maker understand technical issues. The expert does not advocate for the side that paid the bill.

The duty to the court is paramount and overrides any duty to the retaining party. That principle is settled across every Australian court and tribunal that deals with residential building work. Get the duty wrong and the report is given little weight, the witness is criticised in the published reasons, and the builder who briefed the witness loses the case.

The Ikarian Reefer principles

The modern statement of an expert's duties comes from National Justice Compania Naviera SA v Prudential Assurance Co Ltd, known as the Ikarian Reefer. Cresswell J set out the duties that have since been adopted into Australian practice notes, court rules and tribunal procedural directions. The core principles are these.

Expert evidence presented to the court should be the independent product of the expert, uninfluenced as to form or content by the exigencies of litigation. An expert should provide independent assistance to the court by way of objective unbiased opinion on matters within their expertise. An expert should state the facts or assumptions on which the opinion is based and should not omit material facts that detract from the opinion. An expert should make it clear when a question or issue falls outside their expertise. If the opinion is provisional because of insufficient data the expert should say so. If the expert changes view after exchanging reports or after reading the other side's report the change should be communicated to the other party and to the court.

Those principles are now baked into every Australian expert evidence regime.

The codes that apply

In the Federal Court the regime is the Expert Evidence Practice Note GPN-EXPT, which annexes the Harmonised Expert Witness Code of Conduct. Every expert giving evidence in the Federal Court must read the Code and agree to be bound by it. Reports must annex the Code with the expert's acknowledgment.

In NSW the relevant instrument is Schedule 7 of the Uniform Civil Procedure Rules 2005, which sets out the Expert Witness Code of Conduct. The Code applies in the Supreme Court, District Court, Local Court and NCAT where directed. NCAT routinely directs that experts in home building matters comply with the UCPR Code or an equivalent tribunal practice direction.

In Victoria, VCAT directs experts to comply with its Practice Note PNVCAT2 Expert Evidence which adopts substantially the same duties. The Supreme Court of Victoria operates under Order 44 of the Supreme Court (General Civil Procedure) Rules.

In Queensland, QCAT's procedural directions and the Uniform Civil Procedure Rules 1999 (Qld) Chapter 11 Part 5 govern expert evidence in building disputes that escalate from QCAT to the courts. Each state and territory has an equivalent code or rules-based regime.

What the code requires in practice

Every report must state the expert's qualifications, the facts and assumptions on which the opinion is based, the questions asked of the expert, the reasoning that links the facts to the conclusions and any matter that is in the expert's specialised knowledge. A report that gives a conclusion without exposed reasoning is not an expert report. It is a bare assertion and a tribunal can refuse to admit it.

The expert must declare any conflict of interest. Common conflicts in residential building disputes include past work for the builder, past dealings with the homeowner's certifier, or a financial interest in a downstream rectification contract. The conflict does not always disqualify the expert but it has to be disclosed up front.

Conclaves and joint reports

In residential defects matters NCAT, VCAT and QCAT often direct a conclave of experts before hearing. The experts meet without the parties, often without lawyers present, and produce a joint report or joint Scott Schedule that records what they agree and what they still disagree about. Conclaves only work because the experts are bound by the duty to the court. An expert who arrives at conclave and refuses to budge on positions that are not defensible loses standing with the decision maker.

How a builder should brief an expert

The brief must be in writing. It must set out the questions the expert is to answer and provide the documents the expert needs. It must not include argumentative framing about why the builder is right. That framing taints the report and gets quoted back against the witness in cross-examination.

The retaining party can discuss factual matters with the expert and explain the contract and the construction sequence. The party cannot script the conclusions. An expert whose report reads as a builder's submission gets cross-examined on independence and loses credibility on the first technical point.