The Expert Witness Code of Conduct in Australia — a plain-English guide

Every expert witness engaged in Australian civil proceedings owes a paramount duty to the court — not to the party paying their fees. That duty is codified in a formal Expert Witness Code of Conduct, which sits as a schedule to the rules of each superior court. Compliance is not optional: a report that does not acknowledge the Code is routinely refused, discounted or ruled inadmissible.

What the Code requires

Across the federal and state schemes the wording differs but the substance is consistent. An expert must be independent, must confine opinion to their genuine field of specialised knowledge, must set out the factual assumptions and reasoning behind each opinion, and must qualify any opinion that is preliminary or based on incomplete data.

• Paramount duty to the court — overriding any obligation to the instructing party.
• An acknowledgement that the expert has read the Code and agrees to be bound by it.
• A statement of qualifications, experience and the questions the expert was asked to address.
• The factual assumptions relied on, and the material examined, tested or inspected.
• The reasoning connecting facts and assumptions to each opinion expressed.
• Any matter that would materially alter the opinion if it changed.

Where the Code sits in each jurisdiction

The federal courts and every Australian superior court publish their own version. The wording varies but the duties are effectively identical.

• Federal Court of Australia — Expert Evidence Practice Note (GPN-EXPT), incorporating the Harmonised Expert Witness Code of Conduct.
• Supreme Court of NSW — Uniform Civil Procedure Rules 2005 (NSW), Schedule 7.
• Supreme Court of Victoria — Supreme Court (General Civil Procedure) Rules 2015, Form 44A.
• Supreme Court of Queensland — Uniform Civil Procedure Rules 1999 (Qld), Chapter 11 Part 5.
• Supreme Court of WA / SA / TAS / ACT / NT — equivalent rules and practice directions in each jurisdiction.
• Tribunals — NCAT, VCAT, QCAT, SACAT, SAT and equivalents each adopt or mirror the Code through their expert evidence procedural directions.

Common Code breaches that damage a case

• Straying outside expertise. A structural engineer opining on waterproofing membranes without membrane-specific experience is easily discredited under cross-examination.
• Advocacy language. Adjectives like clearly, obviously and plainly signal advocacy rather than independent reasoning.
• Assumed facts not identified. If the assumption is not stated, the opinion is untethered from evidence and open to challenge.
• No acknowledgement of the Code. Reports without the acknowledgement are commonly refused admission.
• Conflict not disclosed. Prior involvement with a party, the site, or the design must be disclosed even if the expert considers it immaterial.

How to instruct an expert who will comply

The best predictor of a Code-compliant report is a Code-aware brief. A well-drafted letter of instruction sets out the questions with precision, identifies the material provided, states the assumed facts, and expressly reminds the expert of their overriding duty to the court.

• Frame each question as a discrete issue the expert can answer within their discipline.
• Provide the pleadings, key correspondence, contract documents and any prior expert material.
• Ask the expert to identify any further information required before finalising opinions.
• Request a draft that can be reviewed for scope and clarity before it is finalised.

When to instruct — and when not to

An expert witness is not the right tool for every dispute. For minor residential defect matters under tribunal thresholds a scope-of-works report from a suitably qualified builder or building consultant may be sufficient. Instructing an expert becomes appropriate when causation is contested, where a Scott Schedule is required, where insurers or statutory duty of care claims are in play, or where the matter is likely to proceed beyond conciliation.