What Johnstone v Fawcett’s Garage means for low‑dose mesothelioma claims
Last month the courts returned a careful — and for many, unsatisfying — answer to a painfully familiar problem: how do you prove that a relatively small, historical exposure to asbestos actually caused a victim’s mesothelioma? In Alexander Johnstone (Personal Representative of the Estate of Elaine Johnstone) v Fawcett’s Garage (Newbury) Ltd [2025] EWCA Civ 467, the Court of Appeal upheld the trial judge’s conclusion that the defendant’s admitted unsafe practices at a garage workshop produced, at most, a tiny increase in the deceased’s lifetime risk of mesothelioma — about 0.1% — and that this was not a material increase in risk for the purposes of the special causation rule in mesothelioma cases.
The facts in brief
Elaine Johnstone worked from about 1982–1989 in an office adjacent to a garage where mechanics handled asbestos-containing brake and clutch materials. She was diagnosed with malignant mesothelioma in 2018 and died in 2019. The garage accepted that unsafe practices had occurred (creating visible clouds of dust) but denied that those practices were responsible for Mrs Johnstone’s disease. The claimant relied on the “special rule” (Fairchild-style causation for mesothelioma): she had to show the defendant’s breach produced a material increase in her risk of developing the disease.
What the courts decided — the kernel of the judgment
At trial the judge carried out a detailed assessment of epidemiological and exposure evidence. Using the available epidemiological models (notably Hodgson & Darnton and related Peto/Rake data), and expert evidence on background incidence and fibre type, the judge calculated that the defendant’s contribution amounted to an increase in the deceased’s lifetime risk on the order of 0.1%. He held that this was de minimis — not a material increase in risk — and dismissed the claim. The Court of Appeal agreed that the trial judge had been entitled to make those findings on the evidence and accordingly dismissed the appeal.
Two important methodological points emerged from the appellate judgment:
- Direct risk assessment using epidemiological models is a permissible method to address material increase in risk in low‑exposure cases — provided the evidence supports the approach and the assumptions are transparent. The Court of Appeal found no error in principle in the trial judge’s use of Hodgson & Darnton and supporting material.
- The Court of Appeal rejected the “absolute risk / medical significance” approach (sometimes associated with the Bannister line), which would ask whether an expert doctor would regard the incremental chance as medically significant. The Court said that delegating materiality entirely to a clinical judgment of “medical significance” was not appropriate; that approach was ruled out (obiter), although the court did not say that medical evidence can never be relevant.
Why the 0.1% figure matters
That tiny percentage is the legal fulcrum of this case. In mesothelioma tort claims, once exposure by multiple employers cannot be separated, the law has carved out a “special rule” so that a claimant need only show a defendant’s breach materially increased the risk of disease. But “material” is not the same as “any increase”: it must be more than de minimis. In Johnstone the court concluded that a 0.1% lifetime increase — however morally unattractive the defendant’s conduct — did not meet the legal threshold. That makes Johnstone a powerful precedent for defendants in low‑dose exposure scenarios.
Practical implications for other low‑dose mesothelioma claims
- Higher evidential bar for claimants in low‑dose cases. Where exposures are limited, claimants will increasingly need quantitative epidemiological modelling and robust expert evidence linking the defendant’s specific exposure to a materially increased lifetime risk. General assertions of “exposure” without quantified risk estimates will be vulnerable.
- The direct risk route is usable but fact‑sensitive. Courts accepted use of these epidemiological models in Johnstone when applied carefully. But the Court of Appeal was cautious: it did not lay down a single method to be followed in every low‑dose case — judges must assess whether the available data and expert assumptions make the modelling reliable enough for a findings-on-fact exercise.
- Bannister’s “absolute medical significance” is unlikely to be the sole test. The Court of Appeal signalled that the Bannister-style test (solely asking whether a clinician would regard the increase as medically significant) should not displace careful epidemiological assessment. That said, the court’s rejection was not framed as a categorical death knell for the use of medical opinion — medical evidence remains relevant alongside quantitative assessment.
- Defence and insurance strategies strengthened. Insurers and defendants will find Johnstone helpful: it supports a robust, evidence‑led defence in low‑dose situations and gives weight to precise quantification of background risk and fibre toxicity (chrysotile vs amphibole etc.). Expect defendants to press for detailed contemporaneous records, background incidence analyses, and tightly reasoned expert reports.
- Case‑by‑case inevitability. Importantly, Johnstone is not a blanket rule that every small exposure is legally irrelevant. The decision is heavily fact‑dependent — different exposure histories, different fibre types, or better exposure data could produce materially different outcomes. Courts will still have to evaluate the strength of expert evidence and the reliability of any epidemiological extrapolation.
Bottom line
Johnstone v Fawcett’s Garage is a cautious, evidence‑driven ruling: it underlines that, in low‑dose mesothelioma litigation, numbers matter. A tiny, quantified increase in lifetime risk — even where an employer’s conduct was unsafe — may well be legally insufficient. The Court of Appeal accepted epidemiological modelling as a legitimate tool, but stressed careful, case‑specific assessment and rejected an approach that would outsource the materiality question entirely to a clinician’s view of “medical significance.” The decision will be welcomed by defendants and insurers; claimants will need to respond with stronger, more quantitative proof when exposures are small.
What does this mean for someone who has only had a small amount of exposure?
This case, once again, emphases why it is so important to seek expert legal advice in all cases as, despite this judgement, small exposures can lead to successful claims as long as the relevant evidence is obtained.
The quality of evidence is dictated by the experience of the team who are involved in the running of the claim. Initial discussions with HASAG, the information gathering process of the HASAG panel lawyers along with their collective expertise, experience and up to date knowledge of the interpretation and how a case can be best presented are absolutely essential.
It cannot be over emphasised that every case will turn on its own facts and with the correct expert legal representation, justice can and will still be served.
The instruction of specialised expert legal advisors, such as those chosen by HASAG to work with them and their clients, is ever more crucial and absolutely necessary.
