What is Expert Evidence?

by Greg Carter, Commercial Litigation Lawyer in Perth

Where specialised knowledge or skill is required in a Court case, judges (and juries) may require the assistance of a witness who can give an expert opinion.

For example an engineer may be required to give expert evidence on the cause of a building collapse, an aviation crash investigator on the cause of an airline crash, a pathologist on the cause of death, or an experienced doctor on whether a particular medical test was standard practice.

The role of an expert is to provide an objective unbiased opinion to the Court so that it can reach the correct conclusion on the facts.

Accordingly an expert’s paramount duty is to the Court and not to the party who engages the expert.

So an expert witness cannot be an advocate for a party, and expert evidence that is argumentative or adversarial will usually be rejected by the Court. 

To be admitted as expert evidence at common law, 7 rules must be satisfied:

  1. there must be a field of specialised knowledge, meaning that evidence will be excluded if the ordinary person is as capable as anyone of forming a correct view on the subject
  2. the witness must demonstrate that by specified training, study or experience s/he has become an expert in a particular aspect of that field of specialised knowledge
  3. the witness’ opinion must be based wholly or substantially on the witness’ expert knowledge
  4. the witness must identify any assumptions of primary fact on which the opinion is formed. For example the witness may say, assuming facts a, b and c, my opinion is d
  5. the opinion is not admissible unless there is evidence which supports the primary facts on which the opinion is formed
  6. the primary facts must support the opinion
  7. the witness must explain the process of reasoning which leads to his/ her opinion.

An expert report can easily be undermined, for example:

  • if the expert has not been properly briefed with all relevant documents, facts and circumstances
  • the expert has been requested to answer the wrong questions
  • where the above rules are not satisfied
  • communications with the expert reveal that the expert’s independence has been compromised.

If you require assistance obtaining expert evidence please contact me.


Greg Carter is a freelance litigation lawyer based in Perth, specialising in fixed-fee commercial dispute resolution.

Greg offers a FREE consultation and a ‘no obligation’ quotation.

For more information please call Greg on 0422 406 929 or email gc@gregcarter.com.au.

Or see his website www.gregcarter.com.au.


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