Toni Ashby

Questions of causation can be some of the most interesting in law. The test traditionally applied by the UK civil courts on causation is to ask whether “but for” a particular breach of duty, the injury or loss would have happened.

In the 20th century, two further tests were expounded by the courts. These are: whether a particular breach made a “material contribution” to the injury sustained; or whether any breach constituted a “material increase in risk” of the injury being sustained.

In the early 21st century, the House of Lords created, in the English case of Fairchild, an exception to these three, alternative, causation tests, making certain claims easier to pursue. The “Fairchild exception” is a narrow one, with carefully defined criteria, and has never been extended beyond certain asbestos-related claims.

Focusing on Covid-19, causation is considered in the ongoing litigation in Edwards and others v 2 Sisters Food Group Limited. In this case, on 28 May 2025, the High Court at Cardiff overturned a decision of 18 July 2024 by Caernarfon County Court. In doing so, the High Court allowed, subject to any further appeal, certain Covid-19 claimants to take their case to a trial on the evidence.

The claimants in Edwards developed Covid-19 in or around June 2020. They were employed at that time by the defendant in a chicken processing factory. They allege inadequate workplace safety provisions to protect them from development of the disease, also alleging that, in law, those inadequacies caused them to suffer it.

The first court to hear Edwards ruled out any extension of the Fairchild exception and, on 18 July 2024, summarily dismissed the proceedings on the basis that none of the standard tests on causation could be met, regardless of what evidence may subsequently be heard. This was because “ultimately, this workforce was exposed to Covid everywhere, not just in the chicken processing plant”.

The appeal decision of 28 May 2025 agrees the Fairchild exception should not be extended to Covid-19 claims but, nonetheless, reinstated the claims in this case so that evidence could later be heard on them.

Key to the appeal decision was that the first judge to hear the case had, without evidence, discounted the possibility that it could, conceivably and not fancifully, be proven that one or more of the claimants “lived alone, travelled to work alone and had not gone out at all” such that “he or she could prove that their sole exposure to the virus was the workplace”.

Further points made in justifying the appeal decision were that the claimants had “asserted that a very large number of employees at the factory caught Covid-19 over a short period in mid-2020; that they were required to work in very close proximity, shoulder to shoulder with each other, and that the factory was closed shortly thereafter as a result of the intervention of Public Health Wales.”

It will be interesting to see what happens next in the Edwards case. The point remains, though, that with coronavirus particles so small that around 1,000 could fit on the width of a human hair and given the prevalence of such particles during the pandemic, Covid-19 claimants will generally face considerable difficulties in establishing causation.

Toni Ashby is a partner at Clyde & Co. This article first appeared in The Scotsman.