MacDonald, R (On the Application Of) v Secretary of State for Environment, Food And Rural Affairs

The statutory power to slaughter an animal suspected of carrying a prescribed disease confers a broad discretion on the expert decision-maker. Judicial review does not permit the court to resolve competing scientific evidence or substitute its own assessment of risk. An enhanced margin of appreciation applies to scientific, technical and predictive judgments. Intervention requires compelling evidence of irrationality, perversity, unfairness or failure to consider relevant matters. A decision remains lawful where the decision-maker considers the competing evidence, explains why it is rejected and reaches a conclusion reasonably open on the evidence, even if another decision-maker might have reached a different view.

The claimant, the owner of an imported alpaca, sought judicial review of the Secretary of State’s decision to confirm the compulsory slaughter of the animal after two positive serology tests for bovine tuberculosis. She challenged the reliability of the tests, particularly the use of prior skin-test priming, and alleged irrationality, closed-mindedness and failure to consider relevant evidence.

The claim challenged both the decision communicated on 15 July 2018 and the TN03 slaughter notice issued on 21 December 2017 under the Animal Health Act 1981 and related tuberculosis orders. Permission was granted after interim injunctive relief had prevented enforcement. The central issue was whether the Secretary of State had a lawful and rational basis to suspect infection and order slaughter.

1. Claim dismissed. The Secretary of State lawfully exercised the discretion under section 32(1) of the Animal Health Act 1981. The provision was intended to confer a broad discretion on the expert decision-maker responsible for controlling animal disease.
2. The court must not usurp that statutory function or substitute its own view for that of a conscientious expert decision-maker. Where the decision involves scientific, technical or predictive assessments, the decision-maker receives an enhanced margin of appreciation. Judicial review is not an appropriate procedure for determining complex scientific questions.
3. The claimant therefore faced a high threshold. She had to establish compelling evidence that the decision was perverse, unfair or one which no reasonable decision-maker, faced with the evidence, could reach. The disagreement between the parties’ experts about the effect of repeated priming did not approach that threshold.
4. The Secretary of State had considered the warning that the test results should be treated with caution, the absence of clinical signs, the evidence concerning the alpaca’s New Zealand origin and farm biosecurity, and the scientific evidence concerning priming. He gave adequate reasons for rejecting the claimant’s criticisms. His failure to change his view did not show that he had closed his mind.
5. The retest protocol, which required priming and used a more sensitive serological interpretation, rationally prioritised avoiding a false negative because the first positive test had created a strong suspicion of infection. The resulting increase in the possibility of a false positive did not make the decision irrational or perverse.
6. The Secretary of State was entitled to conclude that a further unprimed test would be futile, since a negative result would carry a greater risk of being false and would not remove the evidential significance of the two positive results. The TN03 notice and the later decision were accordingly upheld.

The judgment describes interim injunctive relief granted by Swift J on 16 October 2018 and permission to apply for judicial review granted by Lang J on 6 November 2018. The claim was determined at first instance by the Administrative Court. No appellate decision is stated.