In litigation, evidence is everything. But not all evidence is the same—and neither are the people giving it.
Two categories of witnesses frequently arise in court proceedings: expert witnesses and lay witnesses. Understanding the distinction is crucial, particularly in commercial disputes where the facts are often technical, contested, or outside ordinary experience.
1. What is a Lay Witness?
A lay witness is someone who gives evidence based on their direct observations or involvement in the events of a case. They are typically:
- A party to the dispute,
- An employee or contractor,
- A customer, supplier, or advisor,
- Or a third party with factual knowledge.
Lay witnesses give factual evidence about what they saw, heard, or did. They are not permitted to offer opinions—unless it falls within narrow exceptions, such as giving a general impression of a person’s identity, age, or condition.
For example, a CFO testifying about internal accounting processes during a disputed period is a lay witness—even if they’re highly qualified—because they’re recounting what actually occurred, not offering an expert opinion.
2. What is an Expert Witness?
An expert witness, by contrast, gives evidence because of their specialised training, study, or experience. Their role is to assist the court by providing independent opinion evidence on technical matters beyond common knowledge.
An expert must:
- Be demonstrably qualified in their field,
- Maintain independence and objectivity,
- Comply with formal rules and codes of conduct (such as the Expert Witness Code of Conduct under the Federal Court Rules).
Examples of expert witnesses include:
- A forensic accountant quantifying financial loss,
- A structural engineer assessing building defects,
- A medical specialist evaluating causation or prognosis.
Even though they may be retained by one party, expert witnesses owe their paramount duty to the court—not to the client.
3. How is Someone Classified as an Expert Witness?
Not all specialists or professionals qualify as expert witnesses.
To be classified as an expert by the court, a person must demonstrate:
- Specialised knowledge: Based on training, study, or experience in a recognised field;
- Relevance: Their expertise must directly relate to a matter in dispute;
- Impartiality: They must provide independent analysis, not advocacy.
Expert evidence must generally be provided by way of a formal written report setting out:
- The expert’s qualifications,
- The issues addressed,
- The assumptions relied upon, and
- The basis for their conclusions.
Courts apply strict thresholds. An opinion will not be admissible unless it satisfies the “opinion rule exception” under legislation like section 79 of the Evidence Act 1995 (Cth).
Even highly credentialed professionals may have their evidence excluded if they:
- Overstep their area of expertise,
- Rely on insufficient material, or
- Fail to act independently.
Why the Distinction Matters
The line between expert and lay evidence is not just academic—it has real consequences for how a case is prepared and presented.
Key differences include:
- Admissibility: Lay witnesses cannot provide opinions. Expert witnesses can—but only in their field of expertise and under strict rules.
- Disclosure Requirements: Expert reports must meet prescribed content and procedural standards. Lay evidence is generally simpler and confined to statements of fact.
- Weight of Evidence: Courts assess the reliability and independence of expert evidence carefully. An expert seen as partisan or poorly prepared may be given little or no weight.
Misunderstanding the role of a witness can lead to critical evidence being excluded or undermined.
4. Our View
At Spurling Legal, we understand the strategic importance of deploying the right witnesses—at the right time and in the right way.
In commercial litigation, particularly involving professional negligence, regulatory proceedings, or valuation disputes, expert evidence can be decisive. But it must be carefully framed, disclosed properly, and backed by sound methodology.
We work closely with clients and advisers to ensure that:
- Lay witnesses provide clear, admissible factual accounts, and
- Expert witnesses meet all procedural and evidentiary requirements—while remaining truly independent.
Knowing the difference between expertise and experience can be the difference between winning and losing.
Need clarity on how to use evidence in your dispute?
We assist professionals, directors, and businesses in presenting persuasive, cost-effective cases—built on evidence that stands up in court. Contact us for a confidential discussion.
