Samuel Cuthbert writes about this recent case, which involved issues of material contribution as well as defendant expert evidence which appeared to intentionally paint the claimant in a bad light.
The Claimant suffered a subarachnoid haemorrhage (“SAH”) as a result of a ruptured aneurysm. She made a good recovery from this. She then developed significant Post-Traumatic Stress Disorder (“PTSD”). The ambulance took 109 minutes to reach her. The Defendant admitted a 31-minute negligent period of delay in the ambulance arriving at the Claimant’s house to transport her to hospital. Causation was the only issue in dispute. Specifically, the question to be determined was whether the negligent period of delay caused or contributed of the onset of the PTSD.
HHJ Freedman endorsed the approach to causation set out by Waller J in Bailey v The Ministry of Defence & Anor  1 WLR 1052:
“…I would summarise the position in relation to cumulative cause cases as follows. If the evidence demonstrates on a balance of probabilities that the injury would have occurred as a result of the non-tortious cause or causes in any event, the claimant will have failed to establish that the tortious cause contributed. Hotson exemplifies such a situation. If the evidence demonstrates that ‘but for’ the contribution of the tortious cause the injury would probably not have occurred, the claimant will (obviously) have discharged the burden. In a case where medical science cannot establish the probability that ‘but for’ an act of negligence the injury would not have happened but can establish that the contribution of the negligent cause was more than negligible, the ‘but for’ test is modified, and the claimant will succeed.”
That being so, the position on causation could be summarised as:
i) If it could be shown that the claimant would have developed PTSD irrespective of the negligent period of delay, the claim would fail;
ii) If it could be shown that, “but for” the period of negligent delay, the claimant would not have developed PTSD, the claim would succeed;
iii) If the evidence is incapable of supporting either of i) or ii), then, if it can be shown that the negligent period of delay has made a material contribution to the PTSD, the claim would succeed.
The Expert Evidence
The Defendant’s expert, Dr Bowers, held that the Claimant would have developed PTSD irrespective of the period of negligent delay. Dr Bowers suggested in the expert joint statement that the presence of the Claimant’s mother during the delay period would have attenuated any distressing experience that she had.
The Claimant’s expert, Dr Smith, contended that it would not be possible to identify the point at which PTSD was triggered whilst the Claimant was suffering the SAH. Dr Smith further held that the negligent delay amounted to almost one third of the total period of delay, and that could be said to have materially contributed to the Claimant developing PTSD.
Dr Bowers’ evidence was criticised by HHJ Freedman’s judgment for four reasons. Firstly, in the joint report, Dr Bowers “was at pains to point out that the Claimant had (apparently) significantly minimised the extent of her pre-existing mental health problems.” This had no evidential basis. Secondly, Dr Bowers had been less than fair in pointing to the Claimant’s mobile phone not being charged as an example of her not doing everything to help herself. Thirdly, Dr Bowers made no reference to any literature in his report but stated in cross-examination: “that the literature shows that up to 60% of patients who develop SAH go on to suffer PTSD”. If true, this should have featured in the joint report. Dr Bowers later revised this statistic to between 20% and 60%. Fourthly, Dr Bowers said unequivocally in oral testimony that the Claimant would have suffered PTSD in consequence of the SAH itself. This, however, was not canvassed in the joint statement.
Dr Bowers also suffered more general criticism for his apparent lack of objectivity which manifested an attempt to present the Claimant in less favourable terms. HHJ Freedman held “I do not lightly come to this conclusion” but that such a conclusion was irresistible following the written and oral evidence of Dr Bowers.
Dr Bowers’ radical change in opinion as to when the PTSD was triggered, taken alongside his attempt to paint a negative picture of the Claimant, significantly undermined the court’s confidence in his conclusions.
HHJ Freedman found for the Claimant. He determined this, in line with Dr Smith’s evidence, because medical science is not capable of dissecting the 31-minute period of negligent delay from the rest of the period of the delay so as to enable the inference that PTSD would have occurred irrespective of the 31-minute delay. At  the judge found that: “it is certainly possible that from the moment when the claimant suffered her SAH, she was destined to go on to develop PTSD but to come to such a conclusion, on the balance of probabilities, is a step too far. Put simply, medical science does not permit such a conclusion to be drawn.”
The judge relied upon the judgment of Globe J in Ceri Leigh v London Ambulance NHS Trust  EWHC 286 (QB), which held that, in cases where medical science cannot establish the probability that ‘but for’ the negligent failure the PTSD would have developed, the question becomes whether the contribution of the negligent failure could be established as being more than negligible. If so, the negligence would have made a material contribution to the Claimant developing PTSD.
In consequence, the judge precluded finding either that (i) at the time onset of the SAH, it was likely the Claimant would develop PTSD, or (ii) there was a specific point within the 109 minute period of delay, which, on the balance of probabilities, could be isolated as being the point at which PTSD was likely to develop. Further, given that the period of negligent delay amounted to approximately one third of the overall delay, the judge found at  that: “It would be verging on the absurd, in my view, to suggest that that period of delay when the Claimant was in acute distress, believing that the ambulance was not going to come, did not make a material contribution to the onset of her PTSD.”
The judge further found that an apportionment exercise was inappropriate. This followed from the finding that, in light of the indivisible nature of the injury, it was impossible to say when the trigger for the PTSD occurred.
HHJ Freedman’s criticisms of the Defendant’s expert can be read as a guide to the key pitfalls in expert evidence. Practitioners would be well-advised to ensure that their instructions emphasise the importance of CPR 35.3(2), namely that the expert’s overriding duty is to the court, and that this duty supersedes any obligation to the party instructing the expert.
This judgment also represents a clear expression of the law of material contribution in clinical negligence claims. If the injury would have occurred without the negligence, a claim is likely to fail; where ‘but for’ causation is made out, a claim will likely succeed; however, where neither is the case, if the negligence materially contributed to the injury, such a claim is also likely to succeed.
In this case, the negligent period was around a third of the overall delay. This gives rise to the question as to whether a significantly shorter period of negligent delay would have also been held to have materially contributed to this indivisible injury. As ever, this is likely to turn on the particular facts of a case, as well as on the expert evidence provided to the court.