The High Court ruled that the negligent delay in the arrival of emergency ambulance service made a material contribution to the PTSD suffered by the claimant. The proper approach to causation in this case was a modified “but for” test which looked at whether the contribution of the negligent period of delay to the injury was material.

Key Facts

On 18 September 2016, the claimant suffered a subarachnoid haemorrhage (SAH) when she was on her own at home. She first called the ambulance service at 14.22. Shortly thereafter her mobile phone ran out of battery, and the subsequent calls made by the Emergency Operating Centre went to voicemail. According to ambulance records, it was noted at 15.10 that an ambulance was required within 30 minutes.

Meanwhile, the claimant managed to get hold of her neighbour, who called the ambulance at 15.19 and 15.51. The neighbour also telephoned the claimant’s parents.

At about 16.00 the claimant’s mother arrived at the house and immediately called the ambulance service. The ambulance eventually arrived at 16.11. The claimant was taken to the hospital, where she underwent surgery which proved to be successful. However, she developed significant Post-Traumatic Stress Disorder (PTSD) which was allegedly caused by or attributable to the delay in the arrival of emergency services.

The Legal Issue

It was admitted that there had been a negligent period of delay of 31 minutes. The issue in dispute was one of causation, namely whether the negligent period of delay caused or contributed to the onset of PTSD. To that end, the claimant and the defendant each instructed their own expert psychiatrists to serve as expert witnesses.

The correct approach to causation in “cumulative cause cases” was set out by Waller LJ in Bailey v The Ministry of Defence & Anor (2009). The position is summarised as follows:

1. If it can be shown that the claimant would have developed PTSD, in any event, irrespective of the negligent period of delay, then the claim fails;

2. If it can be shown that but for the period of negligent delay the claimant would not have developed PTSD, then the claim succeeds;

3. If, on the other hand, the evidence is incapable of supporting either of the two propositions set out above, then if it can be shown that the negligent period of delay has made a material contribution to the PTSD, the claim succeeds.

The Decision

Having heard evidence from the claimant, the claimant’s mother, and the experts, the judge concluded that the period of the 31-minute delay made a material contribution to the claimant’s PTSD. The judge considered the theory put forward by the defendant’s expert, that from the moment the claimant suffered SAH she was destined to go on to develop PTSD, a step too far. On the other hand, the judge found considerable force in the proposition advanced by the claimant’s expert that medical science was not capable of dissecting that 31-minute period from the rest of the time the claimant was waiting for an ambulance. Accordingly, it would be an artificial exercise for the court to attempt to determine a fixed point in time where the claimant had suffered sufficient trauma such that she was likely to go on to suffer PTSD. In this regard the judge also made reference to the case of Leigh v London Ambulance NHS Trust (2014), in which Globe J said that it was impossible to predict on any scientific or mathematical bases whether the PTSD would not have developed “but for” the negligent failure of the ambulance to arrive in good time. The key issue was whether the contribution of the negligent failure was more than negligible. Applying that reasoning, the judge in the current case considered that the length of delay, which made up a third of the total waiting time and which occurred when the claimant was in a state of acute distress, made a material contribution to the onset of the claimant’s PTSD.

Finally, on the issue of apportionment, the judge declined to apportion the damages on the basis that PTSD is an indivisible injury. Accordingly, the judge awarded the claimant the sum of £40,000.


The case confirms that the correct approach is that, in cases where medical science cannot establish that “but for” the negligent act the injury would not have happened but can establish that the negligent act contributed materially to the injury, the claimant would succeed on such a modified “but for” test.

It is notable that the judge in this case made a number of observations regarding expert evidence. He noted that while the claimant’s expert was “thoughtful, balanced, and careful”, the same could not be said for the defendant’s expert. This had the effect of undermining the confidence which the court could have in the latter expert’s conclusions. It serves as a reminder for litigants to ensure their experts understand their role in the litigation and their duty to the court, and guard against any bias they may have.

Further reading:

Leach v North East Ambulance Service NHS Foundation Trust [2020] EWHC 2914 (QB)

Bailey v The Ministry of Defence & Anor [2008] EWCA Civ 883

Leigh v London Ambulance NHS Trust [2014] EWHC 286 (QB)