The quality of expert witness evidence

  • Published: March 19, 2019
  • Author: Nigel Poole QC

The Bolam test for clinical negligence is that a healthcare professional is negligent only if they failed to act in accordance with a responsible body of relevant professional opinion. But it is never sufficient for a defendant to defend a claim simply by calling an expert to say that they would have acted in the same way as the defendant. Or that they believe that a body of colleagues would have acted in the same way. 

The Court will always test that evidence. Is it reasonable and logical? Does it reflect a responsible body of opinion within the profession? What is the basis of the opinion, and has the expert reached their conclusions on the basis of a correct understanding of the evidence and by legitimate reasoning?

Judgments in clinical negligence cases

Nearly all judgments in clinical negligence liability trials quote from Bolam and Bolitho. Increasingly, judges are relying on a third case where they have to weigh competing expert evidence: the dicta of Green J, as he then was, in C v North Cumbria University Hospital NHS Trust [2014] EWHC 61.

He said:

"25.  ……….It seems to me that in the light of the case law the following principles and considerations apply to the assessment of such expert evidence in a case such as the present:

i)  Where a body of appropriate expert opinion considers that an act or omission alleged to be negligent is reasonable, a Court will attach substantial weight to that opinion.

ii)  This is so even if there is another body of appropriate opinion which condemns the same act or omission as negligent.

iii)  The Court in making this assessment must not however delegate the task of deciding the issue to the expert. It is ultimately an issue that the Court, taking account of that expert evidence, must decide for itself.

iv)  In making an assessment of whether to accept an expert's opinion, the Court should take account of a variety of factors, including (but not limited to): whether the evidence is tendered in good faith; whether the expert is 'responsible', 'competent' and/or 'respectable'; and whether the opinion is reasonable and logical.

v)  Good faith: An essential element in treating an expert's opinion as valid and relevant is that it is tendered in good faith. However, the mere fact that one or more expert opinions are tendered in good faith is not per se sufficient for a conclusion that a defendant's conduct, endorsed by expert opinion tendered in good faith, necessarily accords with sound medical practice.

vi)  Responsible/competent/respectable: In Bolitho, Lord Brown Wilkinson cited each of these three adjectives as relevant to the exercise of assessment of an expert opinion. The judge appeared to treat these as relevant to whether the opinion was 'logical'. It seems to me that, while they may be relevant to whether an opinion is 'logical', they may not be determinative of that issue. A highly responsible and competent expert of the highest degree of respectability may, nonetheless, proffer a conclusion that a Court does not accept, ultimately, as 'logical'. Nonetheless, these are material considerations.

The following are illustrations. 'Competence' is a matter which flows from qualifications and experience. In the context of allegations of clinical negligence in an NHS setting, particular weight may be accorded to an expert with a lengthy experience in the NHS. This does not mean to say that an expert with a lesser level of NHS experience necessarily lacks the same degree of competence. But I do accept that lengthy experience within the NHS is a matter of significance. 

By the same token, an expert who retired ten years ago and whose retirement is spent expressing expert opinions may turn out to be far removed from the fray and much more likely to form an opinion divorced from current practical reality. A 'responsible' expert is one who does not adopt an extreme position, who will make the necessary concessions, and who adheres to the spirit as well as the words of his professional declaration (see CPR35 and the Practice Direction and Protocol).

vii)  Logic/reasonableness: By far and away the most important consideration is the logic of the expert opinion tendered. A judge should not simply accept an expert opinion; it should be tested both against the other evidence tendered during the course of a trial, and against its internal consistency."

The expert witness's evidence and opinions

There are two other points which arise in this case which I would mention. First, a matter of some importance is whether the expert opinion reflects the evidence that has emerged during the trial. Far too often in cases of all sorts, experts prepare their evidence in advance of trial. They make a variety of evidential assumptions and then fail or omit to address themselves to the question of whether these assumptions, and the inferences and opinions drawn therefrom, remain current at the time they come to tender their evidence in the trial. An expert's report will lack logic if, at the point in which it is tendered, it is out of date and not reflective of the evidence in the case as it has unfolded. 

Building credibility as an expert witness

Secondly, it is good practice for experts to ensure that, when they are reciting critical matters, such as clinical notes, they do so with precision. Having said this, the task of the Court is to see beyond stylistic blemishes and to concentrate upon the pith and substance of the expert opinion. Then, the Court's task is to evaluate the content against the evidence as a whole and thereby to assess its logic. If, on analysis of the report, the opinion is from a person of experience, exhibiting competence and respectability, and it is consistent with the evidence and logical, this is an opinion which a judge should attach considerable weight to.

I have previously noted that this extremely useful passage is being widely adopted, and it was again used by Stewart J in the recent case of Keh v Homerton University Hospitals NHS Foundation Trust [2019] EWHC 548. The judge then went on to assess the parties' respective obstetric experts: Professor Steer for the claimant, and Mr Tuffnell for the defendant. I quote the following passage in full because it provides some very useful pointers to the factors that can undermine an expert's credibility before the Court.

"84. In closing submissions Mr McCullough QC made a number of criticisms of Professor Steer's evidence. It is convenient to set out here a number of these before I turn to the obstetric evidence in detail: 

i) Professor Steer has not been in regular clinical practice (on call and on the labour ward) since August 2007. This is a factor which must be taken into account in evaluating his ability to give reliable evidence of the range of acceptable clinical practice, notwithstanding his continued involvement in research and teaching, including teaching junior doctors about aspects of clinical practice.

ii) Professor Steer gave his views without acquainting himself with the pleadings or witness statements. On the first day of his evidence, he said he had not been supplied with these documents by those instructing him. He was unable to explain properly why he took no steps to obtain those either:

(a) from his knowledge as an experienced expert that they must have existed by the time that he came to sign his report.

(b) when he received the report from Mr Tuffnell, whose report makes reference to those documents.

(c) before he met Mr Tuffnell, in order to be properly prepared for the joint meeting.

(d) at any point before stepping into the witness box.

iii) At the outset of the second day of his evidence, he said that, although he had checked and had in fact been supplied with some, but not all, of the witness statements and pleadings, he did not feel that they added anything factual or material to his view of the events.

iv) The bulk of Professor Steer's professional career has been spent at the Chelsea and Westminster Hospital, which has a very high caesarean section rate: in 2012-13 the highest of any hospital in the country. He did not seem to accept that this might affect his view as to the likelihood of Mrs Keh requiring a section following IOL.

v) Professor Steer gave his view on the factual question of the decision Mrs Keh would have taken if offered a caesarean section on the basis of all the risk factors that he considered were applicable. This was not merely evidence of what proportion of women would and would not elect for caesarean section on the basis of the advice he would have given.

vi) He appeared, on a number of occasions, to be unable to recognise a range of obstetric opinion extending beyond his own. This was illustrated by his criticism of not performing a vaginal examination before the plan to induce labour was agreed. The paper that he himself had cited demonstrated that even in 2015, there was a range of opinion, based on apparently reputable studies, as to the utility of the Bishop Score in decision-making in relation to IOL. Even having been taken to that paper, he seemed unwilling to acknowledge the existence/reasonableness of the alternative view.

vii) It is unexplained how an allegation that it was negligent to induce labour could have been pleaded and reasserted in reply if it was based on a misunderstanding of Professor Steer's view.

viii) In cross-examination, he sought to advance, for the first time, criticisms of Miss Ray in relation to her attendance on 23 September 2013, and thereafter, that there should have been (i) vaginal examination; and, potentially, (ii) examination under anaesthetic, as being likely to lead to a conclusion that the uterus should be removed. 

These criticisms had not been put to Miss Ray, even though Professor Steer had been present throughout the trial. Despite them being obstetric matters, no satisfactory explanation as to why they had not been mentioned previously was forthcoming. It was an inadequate explanation to suggest that they were in some way included in his criticism of the lack of a formal multi-disciplinary meeting. These matters will be considered in more detail below.

85. The criticisms carry weight and must affect the court when assessing the reliability of Professor Steer's evidence." 

Important lessons for expert witnesses

  • An expert should have been in practice at the relevant time but also remain in touch with developments. 
  • The expert must have experience relevant to the matters in dispute. 
  • They should have, and should demonstrate that they have, considered all the relevant factual evidence and the allegations so that they know the issues in dispute. 
  • The expert should be aware of the distinction between opinion evidence within their field of expertise and factual issues for the judge to determine. 
  • They should be able to back up their opinions by reference to published studies or papers where appropriate and available. 
  • The expert should be willing to re-evaluate their opinions when the evidence changes.
  • They should be able to give sound reasons for their opinions. 
  • Consistency and coherence are hallmarks of a reliable expert. Introducing new arguments or opinions for the first time in oral evidence is unlikely to impress the Court. 
  • An expert should be self-aware and, in particular, be able to distinguish between their own practice and preferences, and the range of opinion held by responsible bodies of practitioners, particularly where those might differ from their own. 
  • They should never appear to be acting as an advocate for the party instructing them.

It is the litigator's responsibility to try to ensure that experts adhere to these 'rules'. However, litigators have limited control over experts because they are independent and they report to the Court. In clinical negligence litigation, much depends on the quality of the expert opinion evidence on which a party relies. Parties to litigation and the Courts need good quality expert evidence. It does not come cheap, but it is essential to ensure that justice is done.

***Nigel Poole QC's book, Clinical Negligence Made Clear is a great introduction to clinical negligence law for non-lawyers, lawyers with no experience of clinical negligence, expert witnesses, and doctors who get caught up in litigation. Buy your copy.***

Enjoyed this blog? Take a look at Paul Sankey's blog, '7 classic principles for expert witnesses'.



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