Leigh v London Ambulance Service NHS Trust

In a cumulative-cause case, a claimant may succeed where medical science cannot establish that the injury would probably have been avoided absent the negligence, but can establish that the negligent contribution was more than negligible. The court rejected attempts to divide the development of post-traumatic stress disorder into mathematically equivalent periods or to identify a precise point at which causation became inevitable. The whole traumatic experience, including the negligent delay, was relevant. A later-emerging psychiatric symptom may remain part of the same disorder where the medical evidence establishes a continuous psychological phenomenon. Causation is assessed on the evidence as a whole, including expert evidence, the claimant’s history and the relationship between symptoms.

The claimant dislocated her kneecap on a bus and waited approximately 50 minutes for an ambulance. The defendant admitted a negligent 17-minute delay. The claimant developed post-traumatic stress disorder and dissociative seizures, and sought damages for the resulting psychiatric and psychological injury.

The principal issues were whether the negligent delay materially contributed to the PTSD, whether the dissociative seizures were consequent upon the PTSD or other life stressors, and the appropriate assessment of damages.

1. PTSD causation. The court applied the cumulative-cause principles summarised by the Court of Appeal in Bailey and The Ministry of Defence [2008] EWCA Civ 883. The claimant would fail if the PTSD would probably have occurred without the negligence. She would succeed under the ordinary but-for test if it probably would not have occurred without the negligence. Where medical science cannot establish that probability but shows that the negligent contribution was more than negligible, the claimant may still recover.
2. The PTSD resulted from an indivisible traumatic experience. The evidence did not permit the court to identify scientifically or mathematically the point at which the disorder became inevitable. The references in DSM-IV and DSM-V to severity and duration did not support a calculation that each minute carried equal causative potency. The negligent delay was a material contribution to the PTSD. The claimant therefore succeeded on the first issue.
3. Dissociative seizures. The court preferred Dr Sumners’s evidence. The seizures formed part of a continuous dissociative phenomenon and were an evolution or extension of the claimant’s PTSD symptoms. The later appearance of the diagnostic terminology did not establish a later onset. The claimant’s pre-existing vulnerability supported, rather than defeated, the causal conclusion. The seizures were consequent upon the PTSD and were not caused by other life stressors.
4. Damages. The PTSD was categorised as severe under the relevant Judicial College Guidelines. Judgment was entered for the claimant for £522,379, comprising £60,000 general damages, £116,002 past losses and £346,377 future losses, with interest as specified in the judgment.

not stated in the judgment.