Mather v Ministry of Defence

Factual and Procedural Background

This is an action brought by the Plaintiff, a former employee of the Defendant, claiming personal injuries including multiple sclerosis ("MS") and psychiatric injury allegedly caused by exposure to organic solvents during his employment as a painter and finisher with the Defendant between 1989 and 2003. The Plaintiff alleges that these injuries resulted from the Defendant's breach of duty, negligence, and breach of statutory duty under the Control of Substances Hazardous to Health Regulations ("COSHH"). The Defendant denies breach of duty, negligence, breach of statutory duty, causation, and damage, and contends that the claim is statute barred.

A central issue is whether the Plaintiff can demonstrate that his MS was caused by his work exposure to organic solvents. This includes determining (a) whether such exposure can cause MS (generic causation), and (b) whether it did cause the Plaintiff’s MS (individual causation). The Defendant seeks to have causation tried as a preliminary issue, either by defining a preliminary issue on causation with assumed facts regarding exposure or by formally opening the trial limited to medical causation evidence before deciding other issues.

The Plaintiff opposes a preliminary issue, arguing it would increase complexity and expense rather than reduce them. The Defendant applied on 20 July 2020 for causation to be tried preliminarily, and the matter was referred to a Queen's Bench Division judge experienced in complex trials. An application by the Plaintiff to rely on an addendum report from his occupational hygiene expert was also before the court. The court heard full written and oral submissions on 10 March 2021 and reserved judgment.

Legal Issues Presented

1. Whether exposure to organic solvents can cause multiple sclerosis (generic causation).
2. Whether the Plaintiff’s MS was caused by his exposure to organic solvents during employment (individual causation).
3. Whether causation should be tried as a preliminary issue separate from other liability issues.
4. Whether exposure after certain dates (post-1994 and post-2000) is relevant to causation and breach of duty.
5. The applicable legal test for causation in the context of MS, including whether the disease is divisible or indivisible and the relevance of the "doubling of risk" standard.
6. The appropriateness and implications of splitting the trial into stages for causation and other liability issues.

Arguments of the Parties

Defendant's Arguments

• The Defendant denies breach of duty, negligence, statutory breach, causation, and damage.
• The Defendant asserts that exposure to organic solvents did not cause the Plaintiff’s MS and that the claim is statute barred.
• Exposure after 1994 likely complied with workplace standards and exposure after 2000 is irrelevant because the Plaintiff’s MS likely developed by then.
• The Defendant seeks to try causation as a preliminary issue based on assumed facts regarding exposure, limiting evidence to medical causation.
• Expert medical evidence does not support a causal link between solvent exposure and MS; the Plaintiff must prove that solvent exposure more than doubles the risk of MS.
• MS is an indivisible disease; causation must be established on a "but for" basis, not by material contribution or risk increase exceptions.
• Trying causation preliminarily would save time and costs by potentially ending the case early if causation is not established.
• There is a risk of delay and increased costs from splitting the trial and potential appeals.
• The Defendant contends that the Plaintiff’s application to rely on an addendum report was unnecessary or late and seeks costs accordingly.

Plaintiff's Arguments

• The Plaintiff contends that exposure after 1994 and after 2000 remains relevant to causation and breach of duty.
• The Plaintiff disputes that the "doubling of risk" test applies rigidly in this case and relies on clinical evidence, including Dr Schmierer's opinion.
• The Plaintiff argues MS may not be definitively indivisible and that psychiatric injury may be divisible even if MS is not.
• The Plaintiff raises the possibility that a material contribution test or extension of the Fairchild exception could apply.
• The Plaintiff submits that causation law is pragmatic and context-dependent, citing authorities supporting flexibility in causation tests.
• The Plaintiff views a preliminary issue on causation as a "deceptively attractive short-cut" that risks increasing complexity, delay, and expense.
• The Plaintiff relies on cases cautioning against deciding negligence claims on assumed or hypothetical facts.
• The Plaintiff is willing to separate quantum but prefers that liability issues, including causation, be tried together.
• The Plaintiff seeks to rely on an addendum report from the occupational hygiene expert and has agreed to further expert discussions.

Table of Precedents Cited

Court's Reasoning and Analysis

The court analysed the factual background, medical evidence, and legal principles relating to causation. It recognized that the Defendant's case on causation rests on the absence of scientific proof that exposure to organic solvents can cause MS, and that MS is generally regarded as a disease of unknown aetiology requiring proof that the exposure more than doubles the risk.

The Plaintiff challenged these positions, arguing for a more flexible legal approach to causation, highlighting uncertainties about the divisibility of MS, the potential applicability of material contribution or risk increase tests, and the relevance of clinical evidence.

The court noted the significant factual disputes, including the relevance of exposure after 1994 and 2000, and the overlap between breach of duty and causation issues. It observed that assumptions required for a preliminary issue on causation would be problematic and potentially unsafe without hearing full evidence.

The court considered procedural law on preliminary issues, including the need for precision, agreed facts, and avoiding delay or expense. It found that the complexity and factual disputes in this case, combined with the likelihood of appeals and the risk of inconsistent findings across trial stages, made a preliminary issue on causation impractical.

The court also considered the risk of duplication of evidence and witnesses if the trial were split, as well as the potential for delay and increased costs. It concluded that trying causation together with other liability issues, while separating quantum if appropriate, would better serve the overriding objective of expeditious and fair litigation.

Regarding the Plaintiff’s application to rely on an addendum report from the occupational hygiene expert, the court approved the report's inclusion and ordered further expert discussions to clarify any necessary revisions. It reserved the question of costs related to this application pending further submissions.

Holding and Implications

The court REFUSED the Defendant's application to have causation tried as a preliminary issue separately from other liability issues. It held that:

• The factual and legal complexities, unresolved disputes about exposure periods, and the overlap between breach of duty and causation make a preliminary issue unsuitable.
• Splitting the trial risks increased delay, expense, duplication of evidence, and inconsistent findings, contrary to the overriding objective.
• Quantum issues may be separated for trial, but causation and liability issues should be tried together.
• The Plaintiff may rely on the addendum expert report subject to further expert consultation and possible revision.

The decision directly affects the parties by requiring a single trial of causation and liability issues rather than a staged approach, thereby aiming to avoid procedural inefficiencies and delays. The court did not establish any new legal precedent but applied established principles of case management and causation law prudently in a complex factual context.