Limiting Post-Liability Evidence and Tailoring Nuisance Injunctions in Modular Trials: Principles from Webster & Anor v Meenacloghspar (Wind) Ltd

1. Introduction

This commentary examines the High Court of Ireland’s May 27, 2025 judgment in Webster & Anor v Meenacloghspar (Wind) Ltd & Shorten & Anor v Meenacloghspar (Wind) Ltd [2025] IEHC 300, delivered by Ms Justice Emily Egan. The case arose from complaints by two sets of windfarm neighbors—the Websters and Shorten/Carty—against one of the defendant’s turbines (“T2”), alleging that its wind turbine noise (“WTN”) emitted during sensitive periods amounted to a nuisance. Module 1 established liability; Module 2, the subject of this judgment, was tasked with assessing mitigation evidence, determining admissibility of late-tendered material and crafting an appropriate remedy.

2. Summary of the Judgment

Having held in Module 1 that T2 caused an actionable nuisance during night and quiet waking hours, the court invited the parties to agree mitigation by trial and error. The defendant trialled only a lower-power operational mode (1,600 kW), which marginally reduced blade speed and overall noise levels but left high amplitude modulation (AM), “thump” AM, low-frequency tones and erratic noise pronounced. The defendant also sought to reopen liability by tendering a fresh IOA Reference Method/Phase 2 Report/IEC analysis of 2017 data (“new evidence”), arguing it showed WTN levels complied with 2006 planning guidance limits. The court refused to admit that evidence—finding it could with diligence have been produced in Module 1—and declined to revisit liability. On the merits, the 1,600 kW mode did not abate the nuisance. Applying Shelfer principles, and balancing the public interest in renewable energy, the court ordered a bespoke injunction: T2 must be shut down during sensitive periods at certain wind speeds and restricted to specific lower-power modes at higher speeds. This delivers a nuanced remedy aligned with the court’s findings on when and how nuisance arises.

3. Analysis

3.1 Precedents Cited

Murphy v Minister for Defence [1991] 2 IR 161 – criteria for admitting new evidence on appeal, applied to modular trials (existence at trial, diligence, probable influence, credibility).
Re McInerney Homes Ltd [2011] IEHC 25; IESC 31 – test for new evidence post-judgment must at least match appellate rigor.
Inland Fisheries Ireland v O’Baoill [2015] IESC 45 – findings in earlier modules of a modular trial should not be reopened save in exceptional circumstances.
Hinde v Pentire Property Finance [2018] IEHC 575 – similar two-fold test: importance to outcome and diligence in obtaining evidence.
Lanigan v Barry [2016] 1 IR 656 – injunctions for nuisance must do justice, may exceed planning permissions.
Shelfer v City of London Electric Co [1895] 1 Ch 287 – factors guiding damages in lieu vs injunction.

3.2 Legal Reasoning

The court’s reasoning unfolds in two principal strands:

Admissibility of New Evidence & Re-opening Liability
The court applied the Murphy criteria to the defendant’s late-tendered IOA RM/IEC analysis of 2017 data. It held that (a) the data and methodology were available during Module 1 and could have been presented then, (b) the IEC specification does not fill the “lacuna” of planning guidance on nuisance, and (c) any minor differences between IEC and IOA methods did not justify reopening. The exercise of revisiting liability is “sparingly” reserved for exceptional cases; this was not one.
Mitigation & Remedies in Nuisance
Having found the 1,600 kW mode produced noise reductions (max 2.1 dB) barely perceptible to residents, leaving AM and “thump” unchanged, the court concluded it did not mitigate nuisance. On Shelfer principles, injunction rather than damages was warranted because the harm was ongoing and cannot be fully compensated by “small” damages. The public interest in renewable energy was acknowledged, but outweighed by the need to abate nuisance fairly. The court thus fashioned a tailored injunction restricting or shutting down T2 during sensitive periods classified by wind speed and direction, balancing abatement effectiveness with energy generation.

3.3 Impact

This decision establishes several significant precedents:

Modular Trial Finality: Strict limits on admitting post-liability evidence and reopening earlier modules.
Nuisance Injunctions: Courts can craft meteorology-driven injunctions—tying turbine operation modes to wind speed/direction—rather than generic decibel caps.
Evidence Strategy: Operators must gather and present baseline acoustic data, including propagation, frequency content, background noise levels and modulation characteristics, early in litigation.
Balance with Public Interest: Renewable energy benefits do not automatically trump private nuisance rights; mitigation measures must be reasonably tested before seeking damages in lieu.

4. Complex Concepts Simplified

Modular Trial: Splitting a trial into stages (modules) to decide liability first, then remedy/quantum.
Amplitude Modulation (AM): Fluctuations in noise level (“swish” or “thump”) measured as the decibel difference between peaks and troughs.
IOA Reference Method (IOA RM): A UK Institute of Acoustics protocol for measuring AM, requiring AM present at least 50% of each 10-minute period.
Phase 2 Penalty Scheme: A UK proposal to penalise AM by adding decibels to noise levels; not formally adopted in Ireland.
IEC Technical Specification: A draft international document on wind turbine noise measurement techniques; informative, not normative, and not a substitute for local regulation.
Shelfer Principles: Four-part test guiding whether damages can substitute for an injunction (size of injury, measurability, adequacy of damages, injustice to defendant).

5. Conclusion

Webster v Meenacloghspar (Wind) Ltd crystallises the threshold for reopening liability modules—absent exceptional circumstances or newly unavailable data, courts will not admit late evidence. It also charts a path for crafting effective nuisance injunctions in windfarm disputes by linking turbine operation to relevant wind conditions rather than relying solely on traditional decibel limits. Operators must anticipate both liability and remedy phases by commissioning comprehensive, multi-factor acoustic and meteorological assessments early. This judgment will guide practitioners and windfarm developers in balancing renewable energy objectives with adjacent property rights.