Crown Solicitor's Office

Regulatory and environment Insights expert evidence special knowledge

Issued: 3 August 2022

'In my expert opinion': admissibility of expert evidence in the Land and Environment Court 

(Secretary, Department of Planning and Environment v Namoi Valley Farms Pty Ltd (No 6) [2022] NSWLEC 62)

Key points

  • For expert opinion evidence to be admitted under s. 79 of the Evidence Act 1995 (NSW), the expert must explain how they have applied their specialised knowledge to form their opinions and conclusions.

  • Expert witnesses should provide a comprehensive curriculum vitae, setting out the experts' relevant training, study or experience, especially as it relates to the subject of the evidence being given.


Namoi Valley Farms Pty Ltd (the defendant) was prosecuted by the Secretary, Department of Planning and Environment (the prosecutor) under the Native Vegetation Act 2003 (NSW) for illegal clearing on the defendant's property.

The defendant objected to the admission of two expert reports relied upon by the prosecutor. The reports, both authored by Mr Watts, expressed his opinions about the clearing of vegetation at the defendant's property, based on his analysis of satellite images and aerial photographs.

The issue

At issue was the question of whether Mr Watts' evidence should be admitted as expert evidence pursuant to s. 79 of the Evidence Act 1995 (NSW). This required the prosecutor, as the tendering party, to show that the evidence satisfied two criteria, per Dasreef Pty Ltd v Hawchar (2011) 243 CLR 588:

  1. that the witness must have specialised knowledge based on his or her training, study or experience; and

  2. that the opinion expressed by the witness must be wholly or substantially based on that knowledge. 

Reasoning of the court

In relation to Mr Watts' expertise, her Honour noted that Mr Watts' CV appeared 'somewhat truncated' and did not contain specific information related to his training, experience or knowledge in vegetation mapping, which was the subject of his report. Despite this, her Honour found (at [24]) that his expertise was ultimately demonstrated in his report, taking into account his length of experience and his familiarity with the software programs used based on this experience.

In relation to Mr Watts' methodology, her Honour found that he was not required to explain the fundamental workings of certain software (ArcGIS), because such material in his reports was presented in the software's format (at [25], [31]) and his expertise in applying the relevant software was demonstrated throughout his reports (at [46]). However, her Honour found that Mr Watts' conclusions about vegetation clearing were inadmissible as they did not satisfy the second limb of Dasreef. This is because he did not provide specific detail of how he applied his specialised knowledge to form his opinions and conclusions of changes in vegetation based on his visual inspections (at [26]-[29] and [47]).

Implications for prosecutors

When briefing an expert to give evidence, it is crucial to instruct the expert to, in their report, set out the steps in their reasoning process and how they arrive at any conclusions.

Before seeking to rely on the expert report, the prosecutor should check that the report complies with these instructions.

The prosecutor should ensure expert witnesses produce a detailed CV which clearly sets out any relevant training, study or experience in relation to the subject of, and relevant opinions expressed within, their evidence.


Claudia Pendlebury, Director
02 9474 9406

Paris Donnelly, Senior Solicitor 
02 9474 9220

Sarah Braga, Paralegal 
02 9474 9423

The CSO's Regulatory & Environment practice group specialises in advising and representing agencies in relation to regulatory compliance and prosecutions, statutory interpretation advice in the environment and natural resources context, as well as criminal law, evidence and procedure.

Last updated:

13 Jun 2023

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