Wambura & Ors v Barrick TZ Limited (formerly known as Acacia Mining PLC) & Anor

Permission to adduce expert evidence is exceptional because expert opinion is an exception to the general rule that evidence should be factual. Under Civil Procedure Rules 1998 Part 35, the court must be satisfied both that the evidence is admissible and that it is reasonably required to resolve the proceedings.

Evidence is inadmissible where it offers only subjective opinion rather than assistance from a recognised body of expertise. General guidance on security, human rights and risk management does not automatically require expert interpretation. A judge may assess whether security arrangements and the use of force were reasonable by reference to the evidence and clearly expressed standards. The application should be refused where the proposed evidence is too general, overlaps with factual issues, or would usurp the trial judge’s function.

Fourteen Tanzanian nationals brought personal injury and fatal accident claims arising from alleged shootings, assaults and other uses of force by Tanzanian police operating at or near the defendants’ North Mara gold mine. The claimants sought permission to rely on expert evidence concerning security risk assessment, risk management, risk mitigation, police use of force and relevant international and industry standards.

The defendants opposed permission. They argued that the proposed evidence lacked a sufficiently recognised body of expertise, was unnecessary and would merely provide subjective opinions on factual matters for the trial judge. The issue was whether the proposed evidence satisfied the admissibility requirements and, if admissible, was reasonably required to resolve the proceedings.

1. Application dismissed. The proposed security expert evidence was neither admissible under the applicable criteria nor reasonably required under Civil Procedure Rules 1998 Part 35.
2. The court adopted the structure of the Kennedy criteria: whether the evidence would assist the court, whether the witness possessed the necessary knowledge and experience, whether the witness was impartial, and whether a reliable body of knowledge or experience underpinned the evidence. Failure to satisfy one criterion was sufficient to refuse permission.
3. The proposed terms of reference were persistently too wide and insufficiently filtered. Risk management could not be separated from the factual assessment of whether force was excessive or whether the defendants’ conduct was reasonable. Those were matters for the trial judge on the evidence.
4. The relevant international standards, including the Voluntary Principles on Security and Human Rights and the ISO materials, were generalised and expressed in plain, non-technical language. They did not require expert interpretation. The reasoning in Kesabo, Vilca and Kalma demonstrated that comparable issues could be determined without security expert evidence.
5. The proposed expert’s general experience in security management in the extractive sector in Africa did not establish the necessary expertise for this specific dispute, involving a remote and culturally distinct area where artisanal mining was prevalent. His lack of prior experience as an expert witness was not, by itself, disqualifying, and the court rejected the substantial attack on his impartiality.
6. Although the proposed witness might have relevant factual evidence, that did not make his subjective opinions admissible expert evidence. Since the evidence had not been shown to be helpful, the question whether it was reasonably required in all the circumstances did not arise materially.