SOUTH32 ROYALTY INVESTMENTS PTY LTD -v- IGO LTD [2025] WASC 429 (8 October 2025)

(a) the additional question asked of Mr Hunt and answered by him is not relevant to the issues in the proceedings. On this basis, I decline to grant the plaintiff leave to adduce this evidence;

(b) in its current form, much of Mr Hunt's report is irrelevant and inadmissible. Rather than attempting to disentangle the admissible portions from the inadmissible parts, Mr Hunt should file a new report which addresses these reasons; and

(c) at this stage, I am not able to reach a concluded view as to whether Mr Buck's report is relevant to the issues in these proceedings. Ultimately, this will depend on the proper construction of the relevant agreement, which is an issue properly left for trial. I decline to make any orders in respect of this report.

Legal principles governing admissibility of expert evidence

1. As a general rule, a witness can only give evidence as to matters they have observed.[1] There is an exception to this general rule for experts who can give opinion evidence. The expert must be a witness 'of specialised knowledge, derived from study or experience, on a subject for which unqualified persons require that assistance to form a sound judgment.'[2]
2. The role of an expert is to provide an opinion within the demonstrated field of specialist knowledge of the expert, based on facts which can be clearly identified.[3]
3. In Liyanage v The State of Western Australia, the Court of Appeal summarised the circumstances in which expert opinion evidence will be admissible as follows:[4]

An affirmative answer must be given to at least the following four questions before 'expert' opinion evidence on a scientific subject matter will be admissible:

1. Is the opinion relevant; ie could the evidence rationally affect, directly or indirectly, the assessment of the probability of the existence of a fact in issue in the proceedings?
2. Is a person of ordinary experience unable to form a sound judgment on the subject matter without the assistance of an 'expert' witness with special knowledge or experience in the area?
3. Is the subject matter part of a body of knowledge or experience that is sufficiently organised or recognised to be accepted as a reliable body of knowledge or experience?
4. Has the witness acquired, by study or experience, sufficient knowledge of the subject to render her opinion of value in resolving the issues before the court?

1. Expert evidence is not admissible on matters of 'ordinary human experience'.[5]
2. It is not necessary for expert evidence to be opinion evidence; it can be expert factual evidence.[6] As was noted by Kiefel CJ and Gageler J in Lang v R:[7]

Evidence given by an expert sometimes involves nothing more than imparting expert knowledge and sometimes involves nothing more than giving a technical description of events and processes in which the expert was involved.

1. The issue between the parties concerns the proper construction of an agreement for sale of assets and mining tenements entered into between WMC Resources Ltd (WMC) and Southstar Resources NL on 1 August 1997 (Agreement), and whether any royalty is payable by the defendant to the plaintiff on gross revenues realised from its mining operations at the Tropicana gold mine. By reason of a series of deeds of assignment and assumption, the plaintiff has succeeded to WMC's rights and obligations under the Agreement, and the defendant to Southstar Resources NL's.
2. Much of the contest between the parties concerns the proper construction of cl 4.3 of the Agreement, which relevantly provides that:

In consideration of the sole and exclusive right to the Samples, subject to [WMC Resources'] existing obligation pursuant to the Stockdale Joint Venture, in the event that it can be demonstrated that the Sample leads to a discovery of Minerals then [Southstar Resources] agrees to pay to [WMC Resources] a royalty of 1.5% of the Gross Revenue from any mining operations carried out within the Sample Area ('the Sample Royalty').

1. 'Minerals' is defined in the Agreement to have the same meaning as under the Mining Act 1978 (WA) and specifically includes gold.
2. On the face of this clause, two factual issues will need to be determined at trial. First, whether the 'Samples' led to a discovery of gold. Second, if the answer to the first question is 'yes', whether mining operations are carried out within the Sample Area for the purposes of calculating any royalty.

1. Mr Hunt's report addresses six separate questions.
2. The first and second questions address what process or steps he would expect a company, if it acquired access to a database and samples of the same nature and scope as the WMC Diamond Database and Samples, to have followed to use the database and samples. In my view, these questions are not relevant to the matters I am required to determine at trial.
3. Under the terms of the Agreement, the relevant question is whether the plaintiff has demonstrated that the Samples led to a discovery of gold. I do not consider that Mr Hunt's opinion as to how the WMC Diamond Database and Samples could have been used by the defendant is relevant to this issue. The issue is whether these were, in fact, used. While there are a number of paragraphs in these sections of Mr Hunt's report (such as the description of the WMC Diamond Database and Samples, as well as the explanation of a geographic information system (GIS) system) which are admissible, much of his answer is not.
4. In his answer to question three, Mr Hunt was asked to explain, based on his analysis of the documents or facts and assumptions provided, the process or sequence of steps that was taken in the process that led to the discovery of gold which resulted in establishment of the Tropicana gold mine. This question is clearly relevant to the issue as to whether a royalty is payable, as it seeks to demonstrate what steps led to the relevant discovery. I accept this requires Mr Hunt to examine the records of the defendant to ascertain what occurred and to explain this in his report. However, in my view, the way Mr Hunt has addressed this question is not responsive to the question he was asked and is not in an admissible form. Instead of explaining the process or steps taken by the defendant by reference to the documents or facts provided to him, Mr Hunt has provided a commentary on the documents, including expressing opinions on what certain documents mean or why certain matters are important.
5. In my view, Mr Hunt may use his expertise to identify and collate facts, which might otherwise be obscure, in a logical sequence to demonstrate what led the defendant to the discovery which became the Tropicana gold mine. However, this does not extend to Mr Hunt quoting the contents of the documents (which are readily identifiable by the court) or expressing an opinion as to what these documents mean. In my view, this section of Mr Hunt's report must be rewritten.
6. In question four, Mr Hunt was asked whether the term 'discovery' has any industry meaning and the point at which a 'discovery' of gold occurred. Mr Hunt's opinion is that the word 'discovery' has a meaning within the exploration industry. In my view, the plaintiff is entitled to adduce this evidence. Whether Mr Hunt's opinion on this topic is accepted or not is a matter for trial, after all evidence has been adduced and the parties have had the opportunity to present their cases. However, I do not accept that there is any issue on the pleadings as to when the discovery of gold occurred. If the Samples led to a discovery of gold, a royalty is payable on mining operations pursuant to the Agreement. When any such discovery might have occurred does not assist the resolution of either of the issues I have identified at [17]. On this basis, this section of the report should be deleted from any amended report.
7. In section six of the report, Mr Hunt addresses the additional question for which leave is sought. This question is in three parts. For the following reasons, I do not consider these questions are relevant to the issues in the proceedings and refuse the plaintiff's application for leave to adduce this evidence.
8. The first question Mr Hunt addresses is what is meant by the phrase 'major hitherto unrecognised goldfield', a phrase used in the defendant's 2001 prospectus. There is no suggestion that this phrase is a technical term or has any special meaning. On that basis, I do not consider that this is an appropriate question for an expert.[8] If the prospectus and this phrase are relevant to the issues in the proceedings, the court can determine the phrase's meaning without the assistance of expert evidence.
9. The remaining two questions address the extent to which the tenements comprising the Tropicana gold project incorporated a 'major hitherto unrecognised goldfield' at two specific times, and the nature and geographical extent of the project. In my view, these matters are also not relevant to the issues that require determination at trial, as identified at [17] above. While the geographical extent of the Tropicana gold project may be relevant to the determination of whether mining was carried out within the Sample Area, this is not addressed by Mr Hunt in his report. Instead, Mr Hunt expresses opinions as to how the gold deposit was formed, whether there are likely to be multiple 'mineralised events' within the broad vicinity of Tropicana, and the possibility of any development of these deposits. None of these matters are relevant to the issues requiring determination.
10. Given these conclusions, rather than rule on the numerous objections taken to Mr Hunt's report, I consider that Mr Hunt should be asked to re-write his report to address only those questions which are relevant to the issues in the proceeding, and to address the issues with section three of his report.

1. Mr Buck's report addresses five separate questions, as set out in Table 2 of the schedule of expert evidence.
2. Senior counsel for the defendant objected to Mr Buck's report in its entirety on the basis that, on the proper construction of cl 4.3 of the Agreement, whether the WMC Diamond Database and any information derived from it led to the discovery of the Tropicana gold mine is not relevant; the question is instead whether the Samples (or any of them) were used in this process. In my view, it is not appropriate to resolve this issue at this time as it will, in large part, depend on the proper construction of the Agreement. At this stage, I am not satisfied that Mr Buck's report is irrelevant or that the plaintiff should be prevented from adducing his report at trial. I note that this ruling does not prevent the defendant from re-raising this objection at trial, or any raising any other specific objection to Mr Buck's report.
3. In addition to this broad objection, senior counsel for the defendant objected to much of Mr Buck's report on the basis that his report is simply a summary of documents and is not expert evidence. While I accept that Mr Buck summarises a number of documents in his report, I do not accept that this means it is not admissible. I accept that it is at least arguable that much of Mr Buck's report is non-opinion expert evidence, which identifies facts that may otherwise be obscure. In my view, Mr Buck's report does not suffer from the same defects as Mr Hunt's report. It does not provide inadmissible comments on the contents of the documents. Instead, by reference to the contents of documents, Mr Buck explains the process adopted by the defendant and why, in his opinion, this is relevant to the issues raised.
4. In addition, the questions that have been asked of Mr Buck do not suffer from the same issues as those posed to Mr Hunt. Given this, I do not consider that, at a high level, Mr Buck's report is objectionable.

(a) the plaintiff's application for leave to adduce additional expert evidence dated 5 August 2025 should be refused; and

(b) Mr Hunt's report in its present form is inadmissible. My preliminary view is that the plaintiff should have the opportunity to file an amended report as soon as possible.

1. At this stage, I am unable to reach a conclusion on the remaining issues raised by the defendant, particularly in respect of Mr Buck's report. To the extent necessary, these matters can be raised again at trial.
2. I will hear from the parties as to the appropriate orders to give effect to these reasons and as to costs.

I certify that the preceding paragraph(s) comprise the reasons for decision of the Supreme Court of Western Australia.

[1] Grubisic v The State of Western Australia [2011] WASCA 147; (2011) 41 WAR 524 [44].

[2] Liyanage v The State of Western Australia [2017] WASCA 112; (2017) 51 WAR 359 [122].

[3] BHP Billiton Iron Ore Pty Ltd v National Competition Council [2007] FCAFC 157; (2007) 162 FCR 234 [185].

[4] Liyanage v The State of Western Australia [122].

[5] RST v The State of Western Australia [2016] WASCA 59 [26].

[6] Kennedy v Cordia (Services) LLP [2016] UKSC 6; [2016] 1 WLR 597 [44], cited with approval by Gordon and Edelman JJ in Lang v R [2023] HCA [29]; [2023] HCA 29; (2023) 278 CLR 323.

[8] See, eg, Re Michael, Ex parte Epic Energy (WA) Nominees Pty Ltd [2002] WASCA 231; (2002) 25 WAR 511 [107].