Enhanced Discovery and Narrowed Witness Disclosure in Group Proceedings: New Guidance from William Mackie v Mercedes-Benz

Introduction

The judgment in William Mackie against Mercedes-Benz Group Aktiengesellschaft and others ([2025] CSOH 29) is a landmark decision from the Scottish Court of Session that addresses complex issues surrounding document recovery and witness identity disclosure in group proceedings. In this case, Mr. Mackie – acting as a representative for a group of claimants – brought a claim alleging that various Mercedes-Benz defendants had installed prohibited defeat devices in their diesel engines. These devices, which allegedly undermined the vehicles’ nitrogen oxide (NOx) emissions control systems, were accused of facilitating a fraudulent misrepresentation regarding compliance with both EU Regulation 715/2007 and Directive 2007/46/EC.

The litigation is characterized by its multifaceted nature, involving issues of environmental regulation non-compliance, alleged fraudulent conduct, and a comprehensive document recovery regime under the group procedure as defined in Chapter 26A of the Rules of the Court of Session 1994. The key parties include Mr. Mackie, representing a class of purchasers and lessees, and a host of corporate defendants responsible for designing, manufacturing, and managing the vehicles and related software systems.

Summary of the Judgment

Lord Sandison’s opinion sets out a detailed analysis of the applications for document production as well as for the disclosure of witness identities. The Court granted orders for the production of documents falling under paragraphs 1 to 5 of the representative party's list (subject to certain clarificatory adjustments) under RCS 26A.21(2)(b)(v). These documents are aimed at revealing certificates of conformity, technical details of emissions control systems, regulatory communications, and recall procedures.

Conversely, the Court refused orders relating to document production in paragraphs 6 to 8, which were deemed tangential to the central claims and raised issues relating to collusive anti-competitive behavior. With respect to witness identity disclosure, the judgment narrows the operation of RCS26A.21(2)(b)(iv). While acknowledging its usefulness to streamline group procedures, the Court painstakingly limited the scope of such orders – especially when terms like “ultimately responsible” risked encompassing an excessively broad and impractical range of individuals. In addition, the Court carefully balanced privacy concerns under Article 8 of the European Convention on Human Rights and the data protection principles of the GDPR.

Analysis

Precedents Cited

A critical precedent referenced in this judgment is Batchelor v Opel Automobile GmbH [2025] CSOH 18. In Batchelor, the Court emphasized the broad powers available in group proceedings when it comes to document recovery. The judgment relied on this precedent in determining that a wide-ranging document disclosure power existed in group claims – but also highlighted that such power must be exercised in a manner directly relevant to the issues in dispute.

The judgment further discusses classic cases such as National Exchange Co v Drew and Civil Service Building Society v MacDougall to illustrate the necessity of a basis in the pleadings for each call for document production. These precedents reinforce the principle that the court’s intervention should only facilitate further clarity and not transform the discovery process into an open-ended fishing expedition.

With respect to witness disclosure, the Court referred to decisions like F v Scottish Ministers and Axel Springer AG v Germany, alongside relevant European Court of Human Rights judgments, notably in Von Hannover v Germany and LB v Hungary. These cases provide guidance on the threshold for interfering with a person’s privacy rights, and they helped the Court establish that limited disclosure solely among opposing counsel does not trigger a serious interference with Article 8 rights.

Legal Reasoning

Lord Sandison’s opinion is characterized by a rigorous and cautious application of group procedural rules within the context of complex corporate litigation. The Court’s reasoning centers on three key principles:

Relevance and Specificity: Orders for document disclosure must relate directly to issues that are in dispute. The Court emphasised that document production should not be used as an exploratory tool beyond the evidence that the pleadings suggest, thus preventing abuse of the disclosure process.
Efficiency and Economy of Litigation: A central concern of the opinion is to avoid undue delays and administrative burdens on the parties. By granting orders on narrowly tailored requests and rejecting those that could lead to the production of an enormous volume of commercially sensitive information, the Court safeguarded the efficient progress of the litigation.
Balancing Privacy with Judicial Need: In addressing the request for witness identity disclosure, the Court carefully balanced the need for access to essential evidence against the potential infringement of individual privacy rights under Article 8 and data protection considerations under the GDPR. The Court held that simple exchange of names and contact details among legal representatives does not reach the threshold of an Article 8 violation.

Furthermore, the judgment underscores that any exercise of the court’s discretion in ordering discovery must be constrained by the requirement for proportionality. The Court elaborated that a witness disclosure order should not be a “fishing expedition” but must be grounded by the specifics of the case – a principle which is likely to shape future decisions in complex group proceedings.

Impact

This judgment sets an important precedent for how document recovery and witness identity disclosure can be approached in group litigation, particularly in cases involving complex technical and regulatory issues. The clear delineation of permissible scope under RCS26A.21 and the emphasis on proportionality will likely guide future judicial scrutiny of discovery requests in mass tort and other class actions.

The decision is expected to:

Enhance judicial control over discovery in large-scale litigation, ensuring that parties request only information directly relevant to their case.
Influence how courts balance the need for effective evidence gathering with the protection of sensitive commercial and personal data, especially in cross-border corporate contexts.
Encourage more precise pleading and specification on the part of parties when seeking broad-reaching orders, thereby minimizing potential delays and administrative burdens in high-stakes litigation.

Complex Concepts Simplified

Several complex legal concepts feature prominently in the judgment:

Defeat Devices: These are software or hardware mechanisms in vehicles that deliberately reduce the performance of emissions controls under certain driving conditions, thereby skewing test results. In this case, the claim was that such devices were used to cheat emissions tests.
Document Recovery under RCS26A: This mechanism allows the court to order production of documents in group proceedings. The judgment clarifies that while the power is extensive, its use is subject to limitations; only documents that are directly relevant and proportional to the dispute should be recovered.
Witness Identity Disclosure: The court’s power here is designed to identify individuals who are central to developing and proving the case. However, the judgment warns against overly broad disclosure orders that would require identifying too many individuals, potentially infringing on privacy rights.
Balancing Privacy (Article 8) and Judicial Needs: The interplay between an individual’s right to privacy and the justice system’s need to gather relevant evidence is delicately balanced by the Court. The decision highlights that the exchange of names among legal representatives is a limited and acceptable interference under the law.

Conclusion

In summary, the judgment in William Mackie v Mercedes-Benz provides incisive guidance on the use of discovery and witness identity orders in group proceedings. The Court’s measured approach in granting document recovery orders – while narrowly tailoring any witness disclosure requirements – reinforces the need for relevance, specificity, and proportionality in litigation involving sophisticated technical and regulatory disputes.

This decision not only clarifies the scope and application of RCS26A provisions but also sets a new benchmark for balancing corporate confidentiality and individual privacy rights with the judicial imperative to effectively adjudicate complex cases. Future litigants and courts alike will undoubtedly refer to this guidance as a critical tool in navigating the challenges posed by mass tort and complex corporate litigation.