The Supreme Court has reviewed the law on expert evidence in Kennedy v Cordia (Services) LLP  UKSC 6. In particular it analysed when an expert can give factual evidence, rather than simply providing an opinion.
A bout of icy weather in Central Scotland in 2010 has resulted in the Supreme Court reviewing the law on expert evidence. On 18th December that year, Miss Kennedy a home carer employed by Cordia (Services) LLP, slipped and injured her wrist while walking to a client’s house.
She sued the company, and called as part of her case a health and safety expert, Lenford Greasly. He was a consulting engineer and a former factory inspector. The company objected to his evidence on the grounds that he did not have any relevant special skill leaning or experience – an objection which was rejected at first instance.
On appeal, the Inner House took a very different view of Mr Greasly’s evidence. Motivated in part by concerns about the proliferation of experts in civil cases, it stated that he should not have been allowed to give evidence that the company had underestimated the risk, and that some sort of anti-slip overshoe should have been provided. It also ruled inadmissible his statements that had he, Mr Greasly, done the risk assessment he would have reached a different conclusion. It was also wrong that he had been allowed to describe his personal use of one particular product, Yaktrax, over an 18-month period.
Further, the Inner House decided that Mr Greasly should not have been allowed to express his view that the relevant regulations had been breached, as that was a legal question which it was the Lord Ordinary’s job to answer.
In Kennedy v Cordia (Services) LLP  UKSC 6, Lord Reed and Lord Hodge (with whom Lady Hale, Lord Wilson and Lord Toulson agreed) overturned these findings. They took the opportunity [paras 34-73] to review what evidence the courts could receive from experts (known as skilled witnesses in Scotland). It was noted that while this was a Scottish case, the approach to such evidence was similar in many common law jurisdictions.
The court set out four considerations governing the admissibility of expert evidence [at 44]:
(i) whether [it] will assist the court;
(ii) whether the witness has the necessary knowledge and experience;
(iii) whether the witness is impartial in his or her presentation and assessment of the evidence; and
(iv) whether there is a reliable body of knowledge or experience to underpin the expert’s evidence.
They distinguished between opinion evidence and factual evidence given by experts.
Opinion evidence, on which most of the case law concentrates, is subject to a threshold of necessity when the four considerations are assessed. Where an expert gives an opinion, a mere assertion is “worthless … what carries weight is the reasoning, not the conclusion”. On occasion, in order to avoid over-complicated language, the expert may express an opinion on the ultimate issue, particularly before an expert tribunal (in this case a judge), which could be expected to understand its responsibility to decide the issue independently.
However the necessity test did not apply to factual evidence especially where an expert could efficiently summarise and present material not gleaned from his or her own experience. It might be that the court could receive the same evidence by calling a large number of factual witnesses but that would be unnecessarily inefficient.
The court identified a number of types of factual evidence which an expert witness might be allowed to give:
- Firstly, factual evidence based on the expert’s personal observation or sensation – in this case Mr Greasly had, among other things, measured the slope on the footpath. There are no special rules for such evidence, and it can be admitted if it is relevant. Mr Greasly’s evidence of his own use of one particular product, Yaktrax, fell into this category.
- Secondly, information from official publications (e.g. HSE guidance on trips and falls) and research literature.
- Thirdly, evidence of the practices of named relevant parties (in this case what other local authorities did about providing anti-slip devices) and of general practice in the field, which Mr Greasly’s was entitled to give as he had considerable experience of advising employers about complying with the regulations.
- Fourthly, the expert’s evidence of what he would have done in the given situation – even if it was one he or she had never actually encountered in practice. While the court stated that there might be occasions where this would be of limited weight, it was not inadmissible per se, and in the circumstances of this case there was nothing wrong with the Lord Ordinary having relied on Mr Greasly’s statement that he would have rated the risk as “substantial” and not “tolerable” as the company had done.
The court was at pains to emphasise that the judgment was not intended to suggest that worries over the cost of experts were exaggerated. However, while this case does not represent a significant change to the admissibility of expert evidence, it is likely to encourage parties to consider instructing them more to give factual, as well as opinion, evidence. This will apply equally to the sphere of professional discipline as to purely civil cases.