The Privy Council has reaffirmed the doctrine of material contribution that was, to some extent, already law in their recent decision in Williams v The Bermuda Hospitals Board. The Council confirmed that where an injury is caused by two or more factors operating cumulatively, one or more of which was a breach of duty, it is immaterial for the purposes of recovering damages for negligence whether the cumulative factors operated concurrently or successively.

The underlying case arose out of a claim for medical negligence. The claimant, Mr Williams, attended

hospital suffering from acute appendicitis. While he had an appendectomy later that day, there were serious complications involving sepsis to his heart and lungs which had developed incrementally over time while he was awaiting treatment in hospital. The original judge found as fact that there had been a culpable delay of at least two hours and 20 minutes prior to the appendectomy, but that the claimant had not proved that the delay was the cause of the complications to his condition. This decision was reversed by the Court of Appeal and that reversal was then endorsed by the Privy Council.

The primary authority for this decision was the House of Lords case Bonnington Castings v Wardlaw. In Bonnington a claimant contracted pneumoconiosis through inhalation of dust containing minute portides of silica during the course of his employment. The dust inhaled by the claimant came from two sources, one of which was the pneumatic hammers in the factory, which involved no negligence on the part of his employers. The second source was the swing grinders in operation at the factory, and the emission of dust was a result of the negligence of the claimant’s employer. The House of Lords concluded that, because the claimant’s condition was caused by the total dust ingested, the important question was whether the dust originating as a result of the employer’s negligence materially contributed to the claimant’s condition.

Given that the conclusion (as a finding of fact) was that the dust from the swing grinders had materially contributed to the claimant’s condition, the employer was held liable for damages arising from the claimant’s entire condition.

The parallels between Bonnington and Williams were obvious. However, it was possible to distinguish Williams from Bonnington because in Bonnington the two causes had occurred concurrently not successively. While the defendant argued that this should be a reason for distinguishing Bonnington, the Privy Council did not agree. They held that it was immaterial whether the factors operating cumulatively were simultaneous or consecutive, even though the two factors in Williams (the appendicitis and the subsequent delay) had occurred consecutively.

It should be noted that while the Bonnington decision was reaffirmed, the Privy Council did not consider the evidential considerations that were important in such cases, although it was held that the sequence of events might be relevant in considering as a matter of fact whether the later event had made a material contribution to the outcome or whether the earlier event had been overtaken by subsequent events. Notwithstanding this position, as a general rule, successive events were capable of making material contributions.

This decision will of course have ramifications for any employer, including those within the aviation sector (for example manufacturing companies or maintenance providers), whose negligent act may have contributed to an employee’s injury. Such employers should be aware that if their employees are capable of demonstrating that a factor, caused by a wrongful act, caused injury and contributed to an overall condition, it does not matter that that condition may have been caused cumulatively by another factor (that may or may not in itself be wrongful). Accordingly, a claimant will succeed in proving causation where he or she can prove, on the balance of probabilities, that a defendant’s negligence has materially contributed to an invisible injury.