Last week’s decision of the United Kingdom Supreme Court, although not a claim about medical treatment, included an overview of the obligations of expert witnesses and lawyers retaining such witnesses: Kennedy v Cordia (Services) LLP  UKSC 6.
In relation to the obligations of the lawyers, as explained further below the court said that the legal team should disclose to the expert not only material which supports their client’s case but also material, of which they are aware, that points in the other direction.
Lords Reed & Hodge (with whom Lady Hale, Lord Wilson & Lord Toulson agreed) addressed expert evidence at  onwards. A detailed summary appears in a note by Gordon Exall.
The court (at ) emphasised the expert’s provision of reasons, not only conclusions:
As Lord Prosser pithily stated in Dingley v Chief Constable, Strathclyde Police 1998 SC 548, 604: “As with judicial or other opinions, what carries weight is the reasoning, not the conclusion.”
On the question of an established body of knowledge, the court at  said:
We agree with that proposition, which is supported in Scotland and in other jurisdictions by the court’s refusal to accept the evidence of an expert whose methodology is not based on any established body of knowledge. Thus in Young v Her Majesty’s Advocate2014 SLT 21, the High Court refused to admit evidence of “case linkage analysis” because it was the subject of only relatively recent academic research and a methodology which was not yet sufficiently developed that it could be treated as reliable. See also, for example,R v Gilfoyle  2 Cr App R 5, in which the English Court of Appeal (Criminal Division) refused to admit expert evidence on “psychological autopsy” for several reasons, including that the expert had not embarked on the exercise in question before and also that there were no criteria by reference to which the court could test the quality of his opinions and no substantial body of academic writing approving his methodology. The court also observed that the psychologist’s views were based on one-sided information and doubted that the assessment of levels of happiness or unhappiness was a task for an expert rather than jurors.
On the role of the lawyers and the briefing of experts, at  the court said:
It falls in the first instance to counsel and solicitors who propose to adduce the evidence of a skilled witness to assess whether the proposed witness has the necessary expertise and whether his or her evidence is otherwise admissible. It is also their role to make sure that the proposed witness is aware of the duties imposed on an expert witness. The legal team also should disclose to the expert all of the relevant factual material which they intend should contribute to the expert’s evidence in addition to his or her own pre-existing knowledge. That should include not only material which supports their client’s case but also material, of which they are aware, that points in the other direction, viz the court’s concerns about one-sided information in R v Gilfoyle. The skilled witness should take into account and disclose in the written report the relevant factual evidence so provided.