Expert Report fails to explain how the opinion was reached: Court of Appeal says it's inadmissible

The most important function of an expert witness is to assist the court (and jury if there is one) to understand technical and scientific matters.   This helps the decision maker to make an informed judgment about technical issues instead of an “act of faith” or merely a guess.

However, experts cannot usurp the role of the judge or jury.   Experts must adhere to the rules of expert evidence.   Otherwise, the court is unable to test the reliability and accuracy of their conclusions.  If an expert does not clearly set out their reasoning process (thereby demonstrating to the court how they applied their “science” to the facts), then they will not have assisted the court.  Instead they will have failed both the court and the party who engaged them.  

This was confirmed by the Queensland Court of Appeal in a decision published in August 2022. In R v Gibson [2022] QCA 151, the expert opinion of a forensic psychiatrist in a criminal matter was confirmed to be inadmissible.     Despite preparing a detailed report, the expert failed to explain how he reached the conclusion that Mr Gibson lacked capacity to understand the ramifications of pleading guilty.    The “absence of a statement of the reasoning by which [the expert’s] opinion was reached with reference to the underlying factual substratum” resulted in his evidence being inadmissible.   

Because of this flaw in his report, the court held that the expert’s conclusions “do not rise above the level of assertion. There is no reference to a factual basis for the conclusions or any reasoning which relates them to the balance of the report which addresses the applicant’s then current mental state”.

A supplementary report by the expert repeated the opinions in the first report but also did not identify any basis for that opinion.    A further email by the expert contained more expressions of his opinion, but again failed to explain how he reached those opinions.

Therefore the Court of Appeal was left with no option but to conclude that “the absence of reasoning made with reference to an identified factual basis for [the doctor’s] opinions required the conclusion that his reports were inadmissible”.  

The requirement of an expert to adequately explain the reasons why they formed their opinion is not new law or a novel concept.  The requirements for admissibility of expert evidence have been part of the common law for a long time and were helpfully summarized in 2001 in decision of Makita (Aust) Pty Ltd v Sprowles (2001) 52 NSWLR 705.      Many expert reports have been rejected because this important requirement was omitted. 

When reports are delivered by experts which merely contain a set of facts and a conclusion but have nothing to link the conclusion to the facts (which demonstrates how their science was applied to facts), the expert is effectively saying to the court “just trust me – I know what I am doing”.   

However, this is not how our judicial system works, and the response will likely be “no thanks”.       

The court cannot accept the conclusions if the expert has not provided the necessary scientific criteria for the court to assess the veracity of the opinions.    

If experts don’t explain their reasoning, then their conclusion might essentially amount to speculation, and experts have no role in the judicial system if their evidence amounts to speculation.  

Courts perform a rigorous role of determining disputes.  Experts need to be equally rigorous in the preparation of their reports.   They also need to demonstrate the rigor that was applied to the scientific or technical issues. 

When experts ignore these requirements, they have failed in their core function (which is to assist the court to understand the scientific or technical issues before the court).     Their role in the litigation is made redundant.  

This can have very serious consequence to the client and the outcome of the litigation.    If the report is held to be inadmissible, the client will have incurred unnecessary legal expenses, may have lost the opportunity to engage an alternative expert who would have done a more rigorous report, and may have lost the opportunity to win their case.    In a criminal case, this may cause the client to lose their liberty.   In a civil case, this may cause the client to lose substantial sums of money.   

It can also have significant reputational consequences for the expert and whether they are invited to provide expert opinions in future matters.  

Experts will only add true value to a matter if they have a clear understanding of their role in the judicial system, the rules of expert evidence, and what is required of them when preparing their expert reports.  

If you want to learn more about how to be a truly effective expert witness, head over to expertwitnesscoach.com where you can enroll in our online course “The Effective Expert Witness”.