Expert evidence – Judge preferring the evidence of one Expert to that of another
EWCA Civ 1261  TEDR Vol 13 Issue 1
Mr Cookson had worked for Novartis in the production of dye-stuffs, including azo-dyes, for some years during the 1960’s. He had developed bladder cancer and alleged that the condition was caused by exposure to carcinogens, in breach of duty, during his employment with Novartis.
Mr Cookson had also been a moderate smoker for many years. He had given up in 1980.
It was accepted by all that occupational exposure to various carcinogens and cigarette smoke were both capable of causing bladder cancer.
On the evidence, the Judge at first instance identified several carcinogenic substances that Mr Cookson would have used and/or been exposed to during his employment.
As to the level of exposure, expert evidence was called on both sides. In brief, the expert for Mr Cookson believed that he had been exposed to carcinogens. He concluded that the exposure had significantly increased the risk of him developing cancer. The expert for Novartis disagreed. He considered that when account was taken of the frequency and duration of the exposure, the daily and cumulative doses would not have exceeded the in-house exposure limits. The Judge accepted that there had been exposure and exposure in breach of duty.
The matter then turned to medical causation.
Expert evidence was given firstly by two Urologists, one for each party.
Mr Cookson’s expert originally dealt mainly with condition and prognosis but expressed the view that long exposure to carcinogens at work was probably responsible.
Novartis’ expert expressed the view that cigarette smoking should be viewed as the cause until other aetiological factors could be established. He felt unable to express a view as to the occupational exposure or its causative potency.
Because causation was a live issue, the parties agreed jointly to instruct an Epidemiologist who had widely published on the issue of bladder cancer.
In his report, he opined that Mr Cookson had only been at a low risk of developing cancer but that, of the two possible causes, the risk of harm from cigarette smoking was greater. In an addendum report, he concluded that the occupational exposure had been very low, albeit he accepted that it was greater than he had originally thought following sight of various other evidence.
Mr Cookson’s Urologist did not agree with the report of the Epidemiologist. He referred to the Epidemiologist’s own published work that the risks due to smoking decreased with the passage of time after cessation. Accordingly, he conducted a review and prepared a full report dealing with the issue.
Mr Cookson’s Urologist and the Epidemiologist were invited to prepare a joint statement setting out areas of agreement and disagreement. The issue between them was on the one hand that the occupational exposure was significant and was the main contributor to the causation of the cancer and on the other that the occupational exposure was so low that the exposure to cigarette smoking must be regarded as the major contributor.
In oral evidence, Mrs Cookson’s Urologist maintained his stand. The Epidemiologist did too but admitted that, when he formed his opinion he had been handicapped by the inaccuracies of his understandings of the exposures. However, he did not consider that these differences gave rise to the need for him to change his mind on the respective contributions of smoking and occupational exposure.
The evidence of Mr Cookson’s Urologist was preferred. It was apparent from the first instance judgment that the Judge considered the unwillingness showed by the Epidemiologist to reconsider his opinion in the light of the new information unimpressive.
The Judge went on to award damages to Mr Cookson.
The Judgment was appealed on several grounds, one of which was that the Judge ought not to have preferred the evidence of an Urologist over that of the real expert in the field, an Epidemiologist. It was argued that, “only he could have a full appreciation of the comparative risks from smoking and occupational exposure as revealed in the published literature”. It was further argued that the literature did not support the proposition that the occupational exposure level revealed by the evidence increased the risk of bladder cancer and the evidence of the Urologist was pure assertion, going beyond his expertise as a clinician. Moreover, because he had worked in Manchester for many years, he had seen many employees with similar problems and was thus too ready to assume that working for Novartis gave rise to an increased risk.
Lady Justice Smith was wholly unable to accept this criticism as follows:
“The proposition that a clinician is not capable of fully understanding the published epidemiological literature on causation of a condition within his own specialty seems unsustainable and would, I think, surprise many clinicians and epidemiologists. In my view it was clear from his detailed reports on causation that”[he].. Was familiar with the published work and he was also able to discuss it intelligently when giving evidence. The Recorder was plainly of that view. As for the suggestion that”[he].. Was too ready to assume that working for the appellant created an increased risk, this was a good “jury point” but, if it did not appeal to the Recorder, that was an end to it”
Once again, this case demonstrates the need to consider the expert and his or her field of expertise, as opposed to their title, when considering what issues they can opine about.
This case also demonstrates the importance of an Expert being prepared to look at the factual evidence in advance of the trial and formulate his or her views as to how the varying factual evidence impacts on their conclusion.
There is nothing wrong in principle with a report drawing two or more conclusions based upon the varying factual bases disclosed by the evidence given that the Judge’s first task will be to decide the factual matrix.
Finally it shows that Judges can and do form adverse views of Experts whom they perceive to be unwilling to consider alternative evidence (or an alternative factual matrix) being put to them in the witness box.