The Public and Commercial Services Union (R on the application of) v Secretary of State for the Home Department

Expert evidence in judicial review is admissible only where it is reasonably required to resolve a pleaded issue. It is seldom required because the court ordinarily examines the legality of the decision or policy and the material before the decision-maker, rather than deciding whether the policy was sensible or safe in practice.

Evidence may assist on technical facts, jurisdictional facts, procedural matters, misconduct, or a serious technical error relevant to irrationality. It remains inadmissible when it merely identifies risks already apparent from the policy documents or witness evidence, expresses opinions on legal questions, or answers the ultimate question of legality. The court should assess necessity, assistance and proportionality in the context of the proceedings as a whole.

Two linked judicial review claims challenged the Secretary of State’s policy for redirecting migrant boats out of UK territorial waters and inducing their return to France. The claimants sought permission to rely on expert reports concerning maritime safety, seaworthiness, navigation, distress at sea, the ordinary practice of seamen and collision regulations.

The Secretary of State opposed admission under CPR 35.1, contending that the pleaded issues concerned the objective meaning and legal effect of the policy, and that the relevant risks were already recognised in the policy documents and factual witness statements. The central issue was whether any part of either report was reasonably required to resolve the proceedings.

1. Applications refused. No part of either expert report was reasonably required to resolve the judicial review proceedings. The judgment expressed no view on the substantive legality of the Pushback Policy.
2. Under CPR 35.1, the court must identify the pleaded issues to which the evidence is said to relate and then assess whether the evidence is reasonably required. The inquiry includes whether evidence is necessary, whether it would assist if not necessary, and whether its admission is reasonably required and proportionate in the context of the proceedings as a whole.
3. Expert evidence is rarely required in judicial review. It may be admissible on matters such as what was before the decision-maker, jurisdictional facts, procedural fairness, misconduct, or a serious technical error relevant to irrationality. The categories are useful but not exhaustive.
4. The reports largely repeated risks already acknowledged in the Policy Statement and SOP, or matters addressed by factual witnesses. Other passages stated common sense conclusions, addressed legal questions, or expressed opinions on the ultimate issues of legality, the applicable Convention and collision rules, distress, and whether the policy was safe or unlawful. Those matters were for the court.
5. The court rejected reliance on the Admiralty Court’s use of nautical assessors. Navigation and seamanship evidence in collision litigation did not alter the distinct task of the Administrative Court, and interpretation of the Collision Regulations was a matter of law.
6. The court considered it premature to decide whether the substantive challenge should be assessed by reference to the approaches in Bibi or Munjaz. Even assuming those submissions were advanced, the reports did not materially assist in evaluating the policy documents. It would also be inappropriate to admit duplicative expert reports addressing essentially the same topic.