The Role of Expert Witnesses in Consent Cases

Articles, News


It is now seven years since the Supreme Court handed down judgment in Montgomery v Lanarkshire Health Board [2015] AC 1430, and although that judgment has significantly changed the legal framework underpinning informed consent claims, the presentation of expert evidence in such cases has been slow to catch up. While expert evidence is still critical to bringing and defending such claims, there is sometimes a lack of appreciation, on the part of both lawyers and experts, of the more limited role of experts where the court is applying the Montgomery rather than Bolam test. This article looks at what is and is not within the remit of experts.

Advising of Risks and Benefits

When the court is considering whether a doctor’s treatment of a patient was negligent, it will of course apply the Bolam test. Expert evidence will in practice often be determinative of that issue. Evidence that the treatment would be supported by a responsible body of clinicians (provided per Bolitho v City and Hackney Health Authority [1998] AC 232 that such evidence is capable of withstanding logical analysis), will, if accepted, be sufficient to establish a defence. This is not so when considering whether there was a negligent failure to obtain informed consent.

The Supreme Court in Montgomery noted the fundamental distinction between on the one hand, the doctor’s role when considering possible investigatory or treatment options and, on the other, her role in discussing with the patient any recommended treatment and possible alternatives, and the risks of injury which may be involved. The former role is an exercise of professional skill and judgment. By contrast the advisory role cannot be regarded as solely an exercise of medical skill and responsibility for determining the nature and extent of a person’s rights rests with the courts, not with the medical professions.

When obtaining informed consent to treatment, doctors owe “a duty to take reasonable care to ensure that the patient is aware of any material risks involved in any recommended treatment, and of any reasonable alternative or variant treatments.” (see Paragraph 87 of Montgomery). In Duce v Worcestershire Acute Hospitals NHS Trust [2018] EWCA Civ 1307 the Court of Appeal clarified that there is a two part test:

  1. What risks associated with an operation were or should have been known to the medical professional in question. That is a matter falling within the expertise of medical professionals.
  2. Whether the patient should have been told about such risks by reference to whether they were material. That is a matter for the Court to determine. This issue is not therefore the subject of the Bolam test and not something that can be determined by reference to expert evidence alone.

    Experts should no longer therefore be commenting on what risks and benefits a responsible body of clinicians would discuss. They should be asked to give an opinion as to what in fact the risks and benefits of a particular treatment are, and also whether these were or should have been known to clinicians at the time of treatment. This evidence will then inform the court’s decision as to whether there was a failure to warn of a material risk.

    The Court of Appeal did not, in Duce, explicitly address the standard to be applied where the court is considering what risks associated with an operation were or should have been known to the medical professional in question. This author would suggest, particularly by reference to paragraphs 83 and 84 of Montgomery, that that is a matter to which the Bolam test will apply.

    Reasonable Alternative Treatments

    The issue of how the courts should determine whether an alternative treatment was reasonable was left open by Montgomery. One possibility was that this was an issue to be determined by reference to the Bolam test, and thus was again a matter for the medical profession. This argument seems, at least for the time being, to have been rejected following the High Court decision in Bayley v George Eliot Hospital NHS Trust [2017] EWHC 3398 (QB). HHJ Worster (the trial judge in Duce), held that it was implicit from the judgment of Lord Kerr and Reed, and explicit in the judgment of Lady Hale, that whether or not the doctor was negligent in failing to inform the patient of a reasonable alternative treatment is not to be determined by the Bolam approach. However, he noted that there was no express guidance in Montgomery as to what is a “reasonable alternative”.

    HHJ Worster considered that he was assisted by considering the approach of the courts in previous cases to the process of assessing what is a material risk. He noted that that issue was not one resolved simply on the expert evidence, but upon an assessment of all the relevant expert evidence. While expert evidence is likely to be a factor, sometimes an important factor, each case will turn on its own facts. Having decided that there was not one threshold at which a treatment became a reasonable alternative, HHJ Worster held that this must be a decision which is sensitive to the particular facts and circumstances of any given case. In his judgment, in that case at least, relevant factors included the patient and her condition at the relevant time, her treatment, the state of medical knowledge about the proposed alternative treatment and the published papers. It will be noted that expert evidence will be relevant to some but not all of these factors.

    It is suggested that experts can usefully give evidence as to the state of medical knowledge of a proposed alternative, the existence of any relevant literature or guidelines and the likely suitability of a particular treatment for the particular patient. They may also be able to assist the court in relation to the availability of the treatment at the relevant time, although this may be a matter for other factual evidence. Once again, however, their opinion as to whether or not a responsible body of clinicians would or would not have advised of the existence of an alternative treatment will be far from determinative of the issue.


    Another commonly encountered issue is experts commenting on what a claimant would have done if given the correct advice. For example, one often sees assertions in reports that on the balance of probabilities the claimant would/would not have agreed to treatment if they had been given the correct advice. This is again a finding of fact for the court and not the expert.

    However, that does not mean that experts have nothing to contribute to issues of causation. They should for example be asked to give detailed evidence as to the risks and benefits of any proposed alternative treatment. This will assist the court in its task of weighing up the likelihood that the claimant would instead have opted for that alternative. Similarly, experts should be asked to give evidence of the likely outcome if the claimant had chosen to do nothing. Evidence of what, in the expert’s experience, most patients do when properly advised may be of some, although relatively limited, value.


    Experts have a valuable role to play in informed consent claims, but there is sometimes confusion as to what that role is. It is the responsibility of instructing lawyers to ask the right focussed questions and to ask experts to remove comments which trespass on the court’s decision making.

    The precise extent of the continuing relevance of Bolam to issues of consent is arguably not entirely clear. What is clear, however, is that reports simply expressing an opinion as to whether there is a responsible body of clinicians who would or would not have advised of a particular risk or alternative treatment are inadequate and do not address the correct tests.

    This article was first published in Medico-Legal Magazine, Issue 21, December 2022

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