The value of expert evidence: medical reporting under the microscope

Expert evidence which is relied upon in a dispute is of greatest value when it is both comprehensive and underpinned by sound reasoning.  

The recent decision in Cruceanu v Vix Technology (Aust) Pty Ltd [2026] NSWPICPD 43 (‘Cruceanu’) serves as a reminder that the outcome of a workers’ compensation dispute is rarely determined based solely on the opinions presented in the expert evidence. Rather, the Commission will look to scrutinise the factual foundation, reasoning and reliability of medical opinions before determining their value.

Where a medical opinion is unjustified or relies on incomplete information, incorrect assumptions or an uncritical acceptance of a reported history, the Commission may place significantly less weight upon it. Conversely, an opinion that carefully identifies the material reviewed, addresses competing evidence and explains the basis for the conclusions reached is usually considered more persuasive.

Background

The dispute arose in the context of a workers compensation claim in which competing medical opinions on causation and the worker’s condition were relied upon by the parties. As is often the case, the experts reached different conclusions regarding the worker's condition and causation. The central issue for determination was not simply which expert held the preferable opinion, but whether the opinions expressed were properly supported by the available evidence and reasoning process.

On appeal, the Presidential Member was required to consider the manner in which the original decision-maker had assessed and reviewed the expert evidence. The decision reinforced that the Commission was not bound to accept an expert's conclusion merely because it is expressed by a qualified medico-legal specialist. Ultimately, it is for the Commission to determine what facts are established and what weight should be given to each piece of evidence. An expert who relies on facts that the Commission ultimately does not accept may find that their opinion carries little evidentiary value.

Why the decision matters

Workers compensation disputes frequently arise out of competing medical opinions. It is often assumed that obtaining a report from a suitably qualified specialist is enough. However, the case law continues to emphasise that credentials alone do not determine the persuasive value of expert evidence. The critical question is whether the opinion is adequately reasoned and based on an accurate understanding of the relevant facts.

The decision in Cruceanu reinforces the important principles in the leading New South Wales Court of Appeal authority on expert evidence in Makita (Australia) Pty Ltd v Sprowles (2001) 52 NSWLR 705. In Makita, Heydon JA notably observed that an expert's opinion is not admissible or persuasive simply because it comes from an expert. The reasoning pathway must be articulated so that it can be evaluated by the tribunal of fact. This case established that an expert opinion is only persuasive where the expert:

·         identifies the facts and assumptions upon which the opinion is based;

·         demonstrates the specialised knowledge relied upon;

·         explains the reasoning process connecting the facts to the conclusion; and

·         shows how that specialised knowledge supports the opinion.

The Commission's approach to expert reports

The Commission has consistently recognised that an expert opinion is only as reliable as the facts upon which it is founded. Where an expert proceeds on an inaccurate, incomplete or untested history, the weight of the report may be significantly reduced. Alternatively, where a specialist carefully identifies the material reviewed, addresses competing evidence and explains their reasoning, the report is likely to carry greater persuasive value.

Best practice for employers and insurers

This decision provides practical guidance for employers and insurers when obtaining expert medical evidence.

1.    Experts should be provided with all relevant records, including:

·         clinical records;

·         treating specialist records;

·         incident reports;

·         witness statements;

·         surveillance material (where applicable);

·         employment records; and

·         prior claims or relevant medical history.

An opinion formed without access to the complete factual picture may be successfully challenged.

2.    Before obtaining an expert opinion, key factual issues and inconsistencies should be identified and tested against the documentary record.

Contemporaneous records often carry significant evidentiary weight. Medical reports may fail to address inconsistencies between a worker's account of events and the contemporaneous documentation.

3.    Scrutinise reports before they are relied upon. Reports should do more than state a conclusion and a persuasive report will explain:

·         the material reviewed;

·         the facts assumed;

·         the medical basis for the opinion; and

·         the reasoning process including why they have accepted or rejected certain evidence or opinion.

Where a report is based primarily on the worker's self-reporting, it should be considered whether such reporting is supported by independent evidence. If specific matters are disputed, these issues should be specifically addressed in the letter of instruction.

Key takeaway

The lesson from Cruceanu is clear. Expert evidence is valuable if it is founded on accurate facts and supported by clear reasoning. The Commission will closely scrutinise the factual assumptions underlying an opinion and determine what weight should be given to the evidence in light of the entire evidentiary history.

For employers and insurers, the decision highlights the importance of briefing, keeping comprehensive evidence and critically evaluated expert reports before relying upon them in litigation.

Authors: Kate Ralph, Caitlin Perritt & Austin Steel

This publication is intended as a source of information only. No reader should act on any matter without first obtaining professional advice.