Elvicta Wood Engineering Ltd & Anor v Huxley

In an occupational disease claim, causation is determined on the balance of probabilities from the evidence as a whole, including epidemiological studies, expert interpretation and the circumstances of the individual case. Medical certainty is unnecessary, although known limitations in statistical evidence must be considered. The Bradford Hill criteria are guidelines for evaluating causation, not cumulative threshold tests. Not every criterion must be satisfied, and a strong factor may suffice. Where competing experts interpret scientific literature, the appellate court should not substitute its own assessment for the trial judge’s evaluation of their expertise and evidence without demonstrable error.

The claimant developed sino-nasal squamous cell carcinoma after prolonged occupational exposure to wood dust. The defendants admitted breach of statutory duty and negligence, but disputed causation because the stronger established association concerned adenocarcinoma rather than squamous cell carcinoma. Thomas J accepted the claimant’s expert evidence and found causation on the balance of probabilities, awarding agreed damages subject to liability. The defendants appealed, challenging the assessment of expert evidence, the treatment of epidemiological studies and the Bradford Hill criteria, and the conclusion on causation. The central issue was whether the judge was entitled to find that the exposure caused or significantly caused the claimant’s disease.

The appeal was dismissed unanimously. Kennedy LJ gave the principal judgment. Buxton LJ agreed and added further observations, and Hale LJ agreed with both judgments. The order was dismissal with costs, subject to legal aid assessment.

1. Causation. The judge was entitled to decide that the defendants’ wrongful exposure to substantial quantities of wood dust caused, or was a significant cause of, the claimant’s squamous cell carcinoma on the balance of probabilities. The court did not have to reach medical certainty. It nevertheless had to recognise the known limitations of epidemiological and statistical material.
2. Expert evidence and appellate review. The trial judge was entitled to assess the competing experts by reference to their relevant expertise, experience, independence and manner of giving evidence. The appellate court could not properly go behind that evaluation or substitute its own assessment where no error had been demonstrated.
3. Scientific evidence. The judge was entitled to act on the evidence presented at trial and was not required to undertake an unaided technical critique of the statistical implications of the studies. If the appellants wished to establish that the Demers study outweighed the other evidence as a matter of statistical expertise, suitable specialist evidence was required.
4. Bradford Hill criteria. The criteria were guidelines or reminders for evaluating whether an epidemiological association supported causation in the individual case. They were not cumulative threshold tests. It was unnecessary for every criterion to receive a positive answer, and some criteria, if sufficiently strong, could be sufficient.
5. Biological plausibility. Buxton LJ observed that a medically plausible mechanism could materially strengthen a case based on statistical association, but could not alone establish causation. The causal connection had to be determined from all the evidence on the balance of probabilities.

1. Court of Appeal (Civil Division): The defendants’ appeal on causation was dismissed with costs, subject to legal aid assessment.
2. High Court, Thomas J: Found that the claimant’s wrongful exposure to wood dust caused or significantly caused his squamous cell carcinoma on the balance of probabilities and awarded agreed damages subject to liability.