Guerrero & 30 Ors v Monterrico Metals Plc

Permission to amend pleadings is governed by the interests of justice and the need to identify the real dispute. Similar-fact or course-of-conduct allegations may be probative of responsibility for a central event, whether they pre-date or post-date it. Their admission must nevertheless be balanced against particularity, cost, delay, disclosure burdens and proportionality. The court may permit an amendment while leaving defects of particularity to be addressed later, including by further information or strike-out. Case management is an active judicial function. Under the overriding objective, the court may exclude issues or take other steps where their investigation is unlikely to yield sufficient probative value to justify the resources required.

The claimants alleged that they suffered torture, unlawful detention and other mistreatment by Peruvian police during protests against a mining project. They sought to amend their Particulars of Claim and Reply to plead earlier and later events as similar-fact evidence and as evidence of a course of conduct by the defendant and its subsidiary.

The Master granted permission to amend, applying the two-stage approach in O’Brien v Chief Constable of South Wales Police—whether the material was potentially probative and, if so, whether its admission would cause unjustness to the defendant. The defendant appealed, contending that the amendments were insufficiently particularised, disproportionate and likely to cause substantial additional cost and delay.

1. Appeal dismissed. The Master was entitled to grant permission to amend. The court’s review respected the case-management discretion entrusted to him, particularly given his detailed familiarity with the proceedings.
2. The proposed allegations in paragraph 52A were capable of falling within the approach in O’Brien v Chief Constable of South Wales Police. Events may have probative value as evidence of propensity or probability whether they occur before or after the principal incident. The Master was also entitled to leave issues of particularity to be addressed through witness statements or further information, with strike-out available later if the deficiencies could not be remedied.
3. The amendments had to be considered in the context of paragraphs 37–42 of the Defence, which introduced the defendant’s alleged community-outreach programme. If those matters were material, fairness required the claimants to be able to meet them and to obtain disclosure. If they were irrelevant, they should not remain in the Defence.
4. The court expressed serious doubts about the probative value and proportionality of paragraphs 37–42 and the related amendments in paragraphs 52B–52E. Evidence of community relations, alleged motive and environmental impact was unlikely to assist materially with the central issues: whether excessive force or unlawful detention occurred and what involvement the defendant had in those acts. Investigation of the alleged diversion of three rivers appeared disproportionate.
5. Those concerns did not justify allowing the appeal. The court could control the proceedings later under CPR 1.1 and CPR 3.1, including by excluding issues or taking other case-management steps. The case management conference was adjourned for further consideration after judgment was handed down.

1. High Court (Queen’s Bench Division): The appeal from the Master’s order dated 20 October 2010 was dismissed. Permission to amend remained in force, subject to later case-management control.