AK v The Secretary of State for Defence

Under the Armed Forces Compensation Scheme, service may be the predominant cause of a claimant’s mental-health injury even where an underlying condition makes the claimant unusually vulnerable to anxiety or stress. The thin skull approach means compensation cannot be refused merely because another person exposed to the same events might not have developed the same condition, symptoms or severity.

A tribunal must identify the relevant process causes, exclude causes that are too remote or uncertain, categorise them as service or non-service causes, and then apply the predominance test. It must make clear findings about the events relied on and must not treat an underlying neurological condition as the predominant cause without separately considering whether service caused the claimed mental-health condition.

AK, a former soldier with autism, claimed Armed Forces Compensation Scheme benefit for mental-health problems which he said arose or worsened during service. The Secretary of State refused the claim, and the First-tier Tribunal dismissed his appeal.

The First-tier Tribunal accepted that AK had experienced inappropriate, unprofessional and offensive behaviour which caused stress. It nevertheless concluded that autism was the predominant cause of his mental-health problems because it affected how he interpreted events. Permission to appeal was granted on grounds concerning worsening, constitutional weakness, the characterisation of the service events, and the no-fault nature of the scheme. The central issue was whether the Tribunal had applied the correct approach to causation and predominant causation.

1. The appeal was allowed. The First-tier Tribunal’s decision involved material errors of law. It was set aside under section 12(2)(a) of the Tribunals, Courts and Enforcement Act 2007.
2. The Tribunal had not clearly identified which alleged service events it accepted. Its findings that AK had experienced inappropriate, unprofessional and offensive behaviour were difficult to reconcile with descriptions of the events as usual, minor or expected. Those inadequate and apparently contradictory findings made the decision difficult to understand and legally unsafe.
3. The proper causation approach, stated in JM v SSD (AFCS) [2015] UKUT 332 (AAC), required the Tribunal to: identify potential process causes; exclude causes too remote or uncertain to be relevant; categorise the relevant causes as service or non-service causes; and, where necessary, apply the predominance test.
4. The Tribunal short-circuited that analysis. It considered whether service caused autism, although AK was not claiming that it did, but did not properly consider whether service was a process cause of his anxiety or depression. A correlation between autism and other mental-health conditions did not establish causation.
5. The Tribunal wrongly treated AK’s possible misinterpretation of social interactions, arising from autism, as the predominant cause of his mental-health problems rather than the service events. The thin-skull approach recognised in JM v SSD (AFCS) meant that unusual sensitivity could not defeat the claim merely because another soldier might have reacted less severely.
6. The ground alleging failure to recognise the no-fault nature of the scheme failed. The absence of an express statement that fault was unnecessary did not, by itself, show that the Tribunal misunderstood the scheme.
7. Further findings of fact were required. The case was remitted under section 12(2)(b)(i) for rehearing by a fresh First-tier Tribunal.

• Upper Tribunal (Administrative Appeals Chamber) — appeal allowed; the First-tier Tribunal decision was set aside and the case remitted for rehearing by a fresh tribunal.
• First-tier Tribunal (WPAFCC) — appeal dismissed and the Secretary of State’s decision confirmed on 9 May 2023, issued 15 May 2023.