Whisky Emissions and Nuisance: Fungal Presence Alone Does Not Prove Actionable Interference

1. Introduction

This judgment addresses the distinction between proving that industrial emissions encourage fungal growth and proving that the resulting interference constitutes an actionable nuisance. Two homeowners alleged that ethanol escaping from Diageo Scotland Limited’s whisky maturation warehouses stimulated the fungus Baudoinia, causing recurrent blackening of their house and garden fixtures.

Lord Young accepted important elements of that account: Baudoinia was present at the property, and its growth was attributable to ethanol emitted from the warehouses. Nevertheless, the action failed. The homeowners had not proved that the fungus substantially contributed to the discolouration complained of. Separately, the court concluded that the interference established by the evidence did not exceed what was reasonably tolerable in the locality.

The decision is therefore not a general rejection of the relationship between whisky maturation and fungal growth. Its significance lies in the additional evidential and legal steps required before that relationship produces liability in nuisance. It also provides substantial guidance on competing scientific evidence, expert independence, locality, self-help measures, public benefit and the proof of damages.

2. Background and Procedural History

The pursuers bought their modern detached house in Bonnybridge in 2002. Its attractions included a community open space and playpark to the front and a nature reserve behind it. Diageo’s bonded warehouse complex, operating since the early 1980s, lay beyond the nature reserve. The nearest warehouse was approximately 370 metres from the house; the complex ultimately comprised nine warehouses.

The homeowners described black deposits appearing shortly after their occupation and worsening around the time additional warehouses were constructed. They reported recurrent staining of external walls, windows, fencing, garden furniture and other outdoor items. Cleaning involved scrubbing, power washing and bleach. They said that both the appearance of the property and the repeated cleaning diminished their enjoyment of their home.

Two neighbouring householders supported the account of recurring blackening and additional maintenance. Diageo disputed causation, the seriousness of any additional discolouration, fault and the losses claimed. Its evidence included photographs of similarly discoloured houses elsewhere in central Scotland and valuation evidence indicating no reduction in the pursuers’ property value.

Proceedings began on 21 February 2014. Earlier procedural decisions were reported at [2017] CSOH 36, [2019] CSOH 63 and [2023] CSOH 43, with an appellate decision at [2024] CSIH 2. Following two discharged proof diets, Lord Young heard evidence over 17 days in 2025, followed by two days of submissions. The present judgment determined the merits after that extensive evidential hearing.

3. Summary of the Decision

Lord Young granted decree of absolvitor in Diageo’s favour and reserved expenses. The defenders did not pursue their prescription pleas, so the judgment did not determine whether the claim was time-barred.

4. Analysis: Scientific Evidence and the Causal Chain

4.1 The court’s task was legal proof, not scientific certification

At the outset of his analysis, Lord Young distinguished the civil standard of proof from scientific proof. A court must resolve the dispute on the balance of probabilities using the evidence available. It neither certifies a scientific proposition for all purposes nor finally settles questions that further research may illuminate.

This distinction worked in both directions. Scientific uncertainty did not automatically defeat the homeowners’ case, but an expert’s plausible hypothesis did not automatically establish a necessary causal link. The court had to assess each proposition separately, applying logic and common sense rather than choosing one scientific discipline or group of experts wholesale.

4.2 Expert admissibility was distinct from evidential weight

Diageo mounted extensive challenges to the admissibility, qualifications and independence of the pursuers’ experts. Lord Young rejected most of them. Several aspects of that treatment are important:

• Specialist reputation did not establish partiality. An expert was not disqualified because his scientific reputation rested substantially on research into the disputed fungus.
• Ordinary commercial work was not a disqualifying financial interest. Payment for testing and the operation of a commercial laboratory did not establish that the expert had an improper stake in the outcome.
• Joint reports were permissible. Two experts could co-author reports where each independently endorsed the conclusions and could explain their respective contributions.
• Advice about investigations was not necessarily advocacy. An expert could properly advise lawyers that a proposed investigation would have limited scientific value.
• Experimental shortcomings generally required evaluation rather than automatic exclusion. The pipe experiment remained admissible, although its design substantially reduced the weight of its conclusions.

The court nevertheless identified genuine limits. It excluded evidence about unpublished research into other Baudoinia species and unpublished panel studies because the defenders lacked adequate notice. The undocumented material also could not be meaningfully evaluated.

Lord Young additionally warned about experts constrained by non-disclosure agreements. Although he did not find that such an agreement had prevented fulfilment of the expert’s duties in this case, contractual restrictions on answering relevant questions could create that risk.

4.3 Microscopy and DNA analysis were not mutually exclusive

Earlier DNA testing in 2012 and 2013 had identified Baudoinia at the property. The principal later dispute concerned samples taken in July 2021. The pursuers’ experts identified the fungus microscopically, whereas Diageo’s DNA expert found substantial amounts in some locations but little or none in others.

Lord Young accepted that a sufficiently experienced and informed mycologist could identify the genus by microscopy. The experts explained distinctive features visible on the slides, including cell walls and reproductive structures. The defenders’ experts questioned the reliability of microscopic identification but did not positively demonstrate that the organisms had been misidentified.

For the house samples, the DNA analysis recorded very low readings corresponding to Baudoinia, which the defenders’ expert treated as possible technical artefacts. The court preferred the positive microscopic evidence because the identifying features had been demonstrated and the assumption underlying the rejection of the low DNA readings had not been further tested.

This was a case-specific assessment, not a ruling that microscopy is generally superior to molecular analysis. Indeed, the court later relied on DNA evidence when considering the diversity of organisms present and the relative importance of Baudoinia.

The court was also dissatisfied with the absence from the evidence of the pursuers’ separately commissioned Jonah Ventures DNA results. It rejected an allegation of suppression, since the results had been disclosed to the defenders. Nevertheless, the explanations for not presenting them were unhelpful. Lord Young declined to speculate about their contents while recognising their absence when evaluating criticism of the defenders’ DNA analysis.

4.4 Ethanol-related growth was proved without direct atmospheric measurements

The court accepted a causal connection between warehouse ethanol emissions and the growth of Baudoinia at the home. The supporting evidence included:

• Longstanding observations associating conspicuous sooty fungal growth with spirits production and maturation.
• Laboratory research showing that certain ethanol concentrations stimulated germination and growth.
• Evidence that approximately 2% of liquid volume evaporated annually during whisky maturation.
• The prevailing south-westerly wind and the house’s position north-east of the warehouses.
• A 2022 sampling exercise showing greater prevalence of Baudoinia near the warehouses and particularly to the north-east and east.
• Internal company correspondence predating December 2002 recognising a connection between the “angel’s share” and blackening on warehouses and nearby houses.

Although the published laboratory work concerned a species not identified in the later Bonnybridge analysis, Lord Young considered it reasonable to infer broadly similar ethanol responses across the closely related species. Their shared association with alcohol-production environments supported that conclusion.

The absence of direct measurements of ethanol at the house was therefore not fatal. This does not make atmospheric monitoring legally unnecessary in every emissions case: it establishes that causation may be proved by a sufficiently persuasive combination of circumstantial, observational and scientific evidence.

4.5 The decisive gap: presence did not establish substantial discolouration

The homeowners’ difficulty arose at the next causal stage. The blackening comprised a complex mixture of organisms, including other darkly pigmented fungi. Establishing that warehouse emissions encouraged one fungus did not establish how much additional blackening those emissions caused.

Descriptions of Baudoinia as “abundant” on microscopic slides were not measurements of its proportion within the material sampled. The DNA analysis showed considerable variation between locations: approximately 41–49% of fungal readings from the shed and 16–80% from the gate were attributed to Baudoinia, whereas the house readings were extremely low. Other dark fungi predominated in the house samples.

The court did not require Baudoinia to be the sole cause. It required proof that its presence substantially contributed to the discolouration alleged to constitute the nuisance. That contribution remained unproved.

4.6 Why the “first coloniser” explanation failed

The pursuers sought to bridge the gap by arguing that Baudoinia first colonised clean surfaces, creating conditions in which other organisms could grow. If established, that explanation might have connected the emissions to a wider blackened microbial community even where Baudoinia itself was not dominant.

The general ecological possibility was not disputed. What was missing was persuasive evidence that this process explained the blackening at this property. There was no published research establishing the proposed role for Baudoinia, and the court found the expert’s unsupported “sense” of the process insufficient.

The 2024 pipe experiment did not fill that gap. A clean plastic pipe placed in the garden developed Baudoinia and visible blackening, unlike a control pipe in Fife. However:

1. The tested material was not adequately representative. Growth on PVC did not establish the same process on the house’s harling or stonework.
2. The control site was insufficiently comparable. Convenience had influenced its selection, leaving environmental differences uncontrolled.
3. The study was too short to establish the proposed ecological sequence. It did not adequately demonstrate the development of the complex community underlying the complaint.
4. The pipe stood close to a known fungal source. Its proximity to the shed might have influenced the result.
5. There was no adequate replication. Repeated monthly sampling of the same experiment was not equivalent to independently repeating it.
6. Sampling by a financially interested litigant was unsatisfactory. The court did not doubt that the pursuer tried to follow instructions, but considered the arrangement a weakness.

These were cumulative weaknesses, not a universal checklist for admissibility. The experiment was a preliminary “proof of concept”, but the court needed evidence capable of supporting the particular causal proposition on which liability depended. The primary basis of dismissal was therefore the failure to prove that warehouse emissions substantially caused the complained-of blackening.

5. The Alternative Nuisance Analysis: What Must a Householder Tolerate?

5.1 An objective, contextual threshold

Although the causation finding disposed of the action, Lord Young separately considered whether the discolouration would have constituted nuisance had the necessary causal contribution been proved. The governing question was whether the interference was plus quam tolerabile: more than reasonably tolerable in all the circumstances.

The homeowners’ disappointment was genuine. The court rejected suggestions that they were abnormally sensitive or had been manipulated by campaigning lawyers. Their sincerity, however, did not establish the objective seriousness required by nuisance law.

Lord Young accepted that bleaching external walls every few years went beyond ordinary expectations. But the evidence concerning the frequency, development and severity of the staining was imprecise. There were few photographs of the house and no systematic visual record before and after cleaning. The available images did not allow the court confidently to assess the progression of discolouration.

5.2 Locality mattered; prior occupation did not create immunity

The area combined residential and light industrial uses. Whisky warehousing was an established and ordinary activity there, and the warehouses predated the housing development.

Their earlier presence did not provide a defence of “coming to the nuisance”. It did, however, inform the character of the locality and what could reasonably be expected within it. The court treated the ordinary and established use of the industrial premises as an important factor, not as a general Scottish rule immunising customary activities.

Photographs of similar discolouration elsewhere in central Scotland also provided context. They did not establish equivalent rates of fungal growth because the cleaning histories were unknown, but they showed that darkening of comparable light-coloured houses was not unique to this estate.

5.3 Aesthetic interference can matter, but its degree must be proved

The complaint concerned gradually accumulating external discolouration, not perceptible ethanol vapour, noise, vibration or offensive smells. The evidence did not establish a health risk. Those circumstances affected the assessment of seriousness, but the judgment did not make health effects or an acute sensory disturbance prerequisites for nuisance.

On balance, the court found interference with enjoyment of the home, but not interference sufficiently serious to exceed reasonable tolerability in this location. This was expressly a finely balanced conclusion.

5.4 Cleaning did not transfer responsibility to the homeowners

Lord Young distinguished the removable nature of the staining from a defence based on the homeowners’ ability to clean it. Removability was relevant context, but self-help was not an important answer to an otherwise established nuisance.

It would be especially problematic to place the burden on householders without examining what reasonable steps the operator could take to reduce emissions. Diageo had produced no evidence of such mitigation. The court therefore resisted converting the reciprocal principle of “give and take” into a situation in which the affected neighbour must bear the entire burden.

5.5 Economic importance was excluded from liability

The court expressly declined to weigh the whisky industry’s contribution to the Scottish and UK economies when deciding whether nuisance existed. Public benefit may influence the remedy, but it does not justify requiring particular neighbours to endure otherwise intolerable interference for a commercial operator’s benefit.

Lord Young’s reference to the “polluter pays” principle reinforced that reasoning. It did not create a separate cause of action or replace the established requirements of Scottish nuisance law.

6. Precedents Cited and Their Influence

6.1 Principal nuisance authorities

Watt v Jamieson 1954 SC 56

This supplied the central Scottish test. The court must balance a proprietor’s freedom to use property against the obligation not to impose material loss or inconvenience on neighbours. The inquiry focuses on the affected proprietor and depends on fact, degree and surrounding circumstances. Lord Young applied its contextual approach rather than demanding that the warehouse use itself be unusual or inherently unreasonable.

Maguire v Charles McNeill Ltd 1922 SC 174

This authority influenced three distinct questions: whether the complained-of source made a material additional contribution; whether interference objectively affected ordinary comfort; and whether evidence from other people in the locality was relevant. It also illustrated why sincere witness accounts might nevertheless overstate the legal seriousness of an interference. Lord Young admitted the neighbours’ evidence but assessed its significance objectively.

Fearn and others v Board of Trustees of the Tate Gallery [2023] UKSC 4

The majority judgment supported the objective assessment of substantial interference, the rejection of self-help as a means of shifting responsibility to the claimant, and the separation of public benefit from liability. Lord Young also noted its treatment of common and ordinary land use, while retaining the Scottish framework in Watt v Jamieson. The defenders’ reliance on the dissenting approach did not persuade him to include economic public interest in the liability assessment.

Sturges v Bridgman 1879 11 Ch D 832

The pursuers cited this against a “coming to the nuisance” defence. The judgment maintained the distinction between impermissible immunity based merely on earlier occupation and legitimate consideration of the locality’s established character.

MacBean v Scottish Water 2020 SLT 707; 2021 SCLR 549; 2021 CSIH 36

Both sides invoked this litigation: the pursuers on tolerability and mitigation, and the defenders on the relevance of public interest. Lord Young did not adopt the proposed economic balancing exercise. His express conclusion was that public benefit did not determine whether nuisance existed.

6.2 Scientific disagreement and expert evidence

Shotts Iron Co v Inglis (1882) 7 App Cas 518

The historical dispute concerned alleged damage to trees from industrial fumes, supported by experts using different scientific investigations. Lord Young drew on it to explain that judges must decide between conflicting scientific accounts as best they can. The parallel was methodological rather than a factual equation between the two alleged pollutants.

Dingley v The Chief Constable, Strathclyde Police 1998 SC 548

This supported the distinction between scientific proof and proof on the balance of probabilities. It also featured in the defenders’ admissibility arguments. Lord Young used it to explain the court’s limited but necessary role in deciding disputed scientific propositions.

Best v The Wellcome Foundation Ltd [1993] ECC 342

This reinforced the need to apply logic and common sense when assessing conflicting scientific evidence, rather than treating scientific uncertainty as preventing adjudication.

Kennedy v Cordia (Services) LLP [2016] UKSC 6

The defenders relied on this as part of their challenge to the experts’ qualifications, independence, reasoning and methodological foundations. The court’s rejection of most objections illustrates the importance of distinguishing evidence that cannot properly assist the court from admissible evidence carrying limited weight.

National Justice Compania Naviera SA v Prudential Assurance Co Ltd (The Ikarian Reefer) (No 1) [1993] 2 Lloyds Rep 68

This formed part of the framework invoked for experts’ duties of independence and proper assistance to the court. The judgment did not treat disputed scientific opinions, co-authorship or ordinary professional payment as themselves breaches of those duties.

Daubert v Merrell Dow Pharmaceuticals Inc (1993) 509 US 579; Amorgianos v National R R Passenger Corp (2002) 303 F 3d 256; General Elec Co v Joiner (1997) 522 US 136

These United States authorities were included in the defenders’ methodological reliability challenge. Lord Young did not separately develop their tests or announce their adoption as a Scottish admissibility code. Their role should therefore not be overstated: the court rejected the broad exclusion sought while critically evaluating the limitations of particular studies.

6.3 Causation and fault

Rhesa Shipping Co SA v Edmunds (the "Popi M") [1985] 1 WLR 948; R (on the application of Thomas Maughan) v Her Majesty's Senior Coroner for Oxfordshire [2019] 1 All ER 561

The defenders cited these against selecting a merely less improbable explanation where the pursuers had not positively proved their case. Lord Young did not undertake an extended analysis of either authority. His conclusions nevertheless separated causal propositions that were proved from the substantial-contribution proposition that remained unsupported.

RHM Bakeries (Scotland) Ltd v Strathclyde Regional Council 1985 SC (HL) 17; Kennedy v Glenbelle Ltd 1996 SC 95

These supplied the requirement of culpa for damages in nuisance. The latter explained that fault extends beyond negligence to forms of knowing or otherwise culpable conduct. Lord Young’s hypothetical finding of fault rested on awareness of the likely consequences and continued operation without sufficient alleviation.

Esso Petroleum Co Ltd v Scottish Ministers & Others [2015] CSOH 21

This supported the proposition that continuing an activity after becoming aware of its nuisance consequences may establish sufficient personal responsibility. It informed the conclusion that, had actionable nuisance been proved, Diageo’s knowledge and conduct would have established culpa.

Webster v Lord Advocate 1985 SC 173

The pursuers relied on this when arguing that a victim’s ability to take remedial steps did not excuse the defender’s conduct. The judgment’s developed treatment of self-help principally drew on the majority reasoning in Fearn and others v Board of Trustees of the Tate Gallery.

6.4 Supporting authorities on mitigation, public interest and damages

• Jones v Ministry of Defence [2021] EWHC 2276 (QB) was cited by the pursuers as a comparison concerning steps taken to minimise nuisance; it did not supply a separate dispositive rule.
• Scott v Leith Commissioners of Police (1830) 8 S 845 was invoked by the defenders on public interest. The court nevertheless excluded the whisky industry’s economic importance from its liability assessment.
• Hunter v Canary Wharf Ltd [1997] AC 655, Drennan v Walsh [2023] NICh 6 and Anthony v Coal Authority [2006] Env LR 17 supported the pursuers’ submissions on loss-of-amenity damages. The court accepted that such damages were conceptually available but proposed a much lower hypothetical valuation.
• Raymond v Young [2015] HLR 41 was relied on by the defenders to distinguish interference with property enjoyment from a standalone claim for personal distress. Lord Young’s hypothetical award was framed as compensation for interference with use and enjoyment and the upheaval of additional cleaning.
• Stevenson v Pontifex & Wood (1887) 15 R 125 supported the availability of further damages proceedings where a nuisance continues. It informed the decision not to propose a speculative award for future loss.

The judgment also drew on Scottish institutional and textbook commentary concerning nuisance, locality and public interest. Neither the Scotch Whisky Regulations 2009 nor planning permission was treated as authorising otherwise actionable interference with neighbouring property.

7. Conditional Findings on Fault and Damages

7.1 Knowledge could have established fault from 2002

Had nuisance been proved, Lord Young would have found culpa established from 2002. Internal correspondence showed that Diageo understood the likely link between ethanol and nearby blackening, even without knowing the precise mechanism.

The court criticised the company’s subsequent stance: its refusal to undertake further investigation requested during the 2009–2010 planning process, its rejection of responsibility for cleaning costs, and the absence of evidence of emission-reduction investigations or effective engagement with residents.

These findings did not themselves establish liability. Knowledge and inadequate engagement could satisfy fault only if the other requirements of the nuisance claim were also proved.

7.2 Loss of amenity did not depend on reduced market value

The pursuers’ valuation expert withdrew support for his reports under cross-examination. The claim for diminution in value therefore lacked evidential support. The defenders’ market evidence also indicated strong demand for houses on the estate.

Lord Young nevertheless rejected the proposition that unchanged market value necessarily excluded loss of amenity. Market price may reflect buyers’ incomplete knowledge, while amenity concerns the occupier’s actual experience of living in the property.

7.3 The hypothetical award was modest

The court did not require an abstract benchmark for average household cleaning costs. Its objection to the expenditure claim was more practical: a long-running action had produced no adequate vouching of the sums allegedly paid.

None of these sums was awarded. They were alternative observations following the dismissal of the claim.

8. Complex Concepts Simplified

Plus quam tolerabile

Interference exceeding what an ordinary neighbour should reasonably tolerate in the particular circumstances and locality.

Culpa

Legally relevant fault. In nuisance, this is wider than careless conduct and may include continuing an activity with knowledge of its harmful consequences.

Balance of probabilities

The civil standard: a proposition must be more likely than not. Scientific certainty is unnecessary, but the necessary links cannot be supplied by speculation.

First coloniser

An organism that establishes itself on a surface before others and may make the surface more suitable for later growth.

Substrate

The material supporting growth, such as plastic, wood, stone or roughcast. A result on one material may not apply to another.

Microscopy and DNA metabarcoding

Microscopy identifies organisms through visible structures; metabarcoding identifies genetic markers within a sample. Their usefulness depends on the question and the reliability of the particular investigation.

Admissibility and weight

Admissibility asks whether evidence may be considered. Weight asks how persuasive it is. Evidence may be admissible yet insufficient to establish liability.

Decree of absolvitor

A final judgment in the defender’s favour on the merits, rather than a merely procedural dismissal.

9. Impact and Limits of the Decision

As an Outer House decision following proof, the judgment’s significance is principally its persuasive reasoning and detailed application of established principles. It does not create a blanket exemption for whisky warehouses or establish that recurrent fungal staining can never constitute nuisance.

For future environmental claims, its central lesson is to distinguish source attribution, biological response, contribution to the complained-of condition, and legally intolerable interference. Success on the first two does not establish the latter two.

The evidential implications are practical. Studies should address the relevant surfaces and causal proposition; controls should meaningfully isolate the suspected influence; and photographs, maintenance records and receipts should document both the interference and the resulting loss. These are lessons from the evidential weaknesses identified, not newly imposed universal formalities.

For industrial operators, the favourable result should not obscure the criticism of Diageo’s knowledge, investigation and community engagement. Neither an activity’s economic importance nor its longstanding presence would excuse an otherwise established nuisance.

Finally, the discussion of expert evidence discourages routine attacks on professional integrity while preserving rigorous scrutiny of methodology. Specialisation is an asset, not evidence of bias; methodological criticism is often a question of weight, not exclusion.

10. Conclusion

The homeowners proved that Diageo’s ethanol emissions encouraged Baudoinia at their property, but not that the fungus substantially caused the blackening alleged to constitute nuisance. The court also found, alternatively, that the interference proved did not exceed reasonable tolerability in the locality.

The judgment’s enduring distinction is between proving an emission-related biological phenomenon and proving actionable interference with property. Its accompanying observations confirm that economic benefit does not excuse nuisance, unchanged market value does not necessarily exclude amenity loss, and expert evidence must be evaluated proposition by proposition.