Is consent to treatment valid?

  • Published: January 19, 2018
  • Author: Paul Sankey, Partner, Enable Law

Has a patient given valid consent to treatment? What is the medical expert's role in reporting on the issue following the Supreme Court's decision in Montgomery v Lanarkshire Health Board in 2015?

Consent to medical treatment: the law

Before Montgomery, the Bolam test applied to medical advice. The advice was adequate if it was in line with what a responsible body of doctors practising the same discipline would have said. For instance, advice by an obstetrician to deliver a baby vaginally would be adequate if a responsible body of obstetricians would have given the same advice – and this was the issue in Montgomery. A patient's consent based on that advice would be valid.

However, the Supreme Court in Montgomery rejected that test in relation to advice. (It remains the test in relation to diagnosis and treatment.) Whether advice was adequate is broadly now what a patient, like this patient, would be expected to want to know. A patient should be presented with the treatment options. The doctor is under a duty to take reasonable care to ensure he or she is aware of the material risks involved in any recommended treatment but also of any reasonable alternative or variant treatments. The test of what amounts to a material risk is whether, in the circumstances of a particular case:

  • a reasonable person in the patient's position would be likely to attach significance to the risk, or
  • the doctor is or should reasonably be aware that the particular patient would attach significance to it.

Patient autonomy

The patient is entitled to decide whether to run a particular risk or not. That decision is not necessarily just a medical one. Patients have different goals and concerns. The impact of a complication will differ from patient to patient: their life circumstances are different. So, imagine two patients considering surgery for a stiff knee. One is an active man in his 30s who goes jogging several times each week and plays football at weekends. He values his active lifestyle and may be happy to face some risks to preserve it. The other is an elderly woman who spends most of her time in an armchair at home. She goes out little and usually travels by car. Recovering good knee function is far less important to her. The two will look at things very differently. But only the patients themselves can really assess the risks and benefits of surgery to them.

The law, as laid down by Montgomery, determines that it is for the surgeon to identify what are the material risks for each patient. The surgeon works out what a reasonable person in each patient's position would want to know and takes reasonable care to ensure that each understands that information. The law expects there to be a process of dialogue, enabling the doctor to understand the patient's concerns and the patient to make an informed decision about what treatment option – if any – to pursue.

Medical advice: two different roles

The Supreme Court identified two distinct roles for the doctor. 

Role 1 involves considering the possible treatment or investigation options and the risks and benefits they bring. This involves medical skill. 

Role 2 involves a judgment about what to discuss with the patient to enable him or her to make her own decision. This is not a uniquely medical judgment. 

The patient's decision will involve non-medical considerations. Those considerations will be different for each patient. The patient is entitled to decide what risks he or she is willing to run. Because making that decision involves non-medical considerations and is sensitive to the characteristics of the patient, assessing the judgment is not a matter simply of medical expertise.

Assessing consent: the task for the medical expert witness

So, the medical expert witness's task is now limited to assessing that first role. The issues a medical expert can address are:

  • the range of reasonable treatment options which a patient should be invited to consider
  • the risks and benefits of those options, bearing in mind both the seriousness of the risk, their medical and functional implications for a patient and the likelihood of the risk transpiring.

What a medical expert is no longer entitled to do is to give evidence on:

  • whether a particular form of treatment should be discussed with patients; or
  • whether particular risks should be discussed with patients.

These are not matters of uniquely medical judgment. They concern a patient's right to make his or her own decision. As the Supreme Court said, "Responsibility for determining the nature and extent of a person's rights rests with the courts, not with the medical professions".

Two recent cases

Two decisions from 2017 help illustrate the role of expert evidence.

(a) Thefaut v Johnson

In Thefaut v Johnson [2017] EHWC 497, a patient was found not to have given valid consent to spinal surgery when the information she was given about its likely benefits was inaccurate. This is an issue that falls into Role 1. Expert evidence was given as to the percentage risks and benefits of surgery and alternative conservative management. That was a matter of medical expertise, based on research about the likely outcomes. The expert evidence suggested that the surgeon had underestimated the risks of surgery, overestimated its likely benefits, and failed to address the benefits of conservative management as an alternative.

(b) Webster v Burton

In Webster v Burton Hospitals NHS Foundation Trust [2017] EWCA Civ 62, an obstetrician failed to advise a mother of the risk of foetal death associated with abnormalities detected on antenatal scans. The extent of this risk and its implication for her management was a Role 1 issue. Whether to discuss it with her was a Role 2 issue.

The trial took place a few months before the Supreme Court decision in Montgomery and the judge therefore applied the Bolam test to the quality of that advice. The defendant's expert thought a reasonable obstetrician would not have attached significance to the association and there was no need to advise the mother. The claimant's expert thought a discussion was only required if the obstetrician had been adopting an unusual course in failing to induce. The implication of his view was that a patient is only entitled to advice where her doctor is adopting an unusual course of action. The Court of Appeal, sitting after the Supreme Court's decision in Montgomery, rejected both views. Assessing whether a risk is material to a patient (Role 2) is not a matter of medical expertise for the medical experts. The mother should have been warned of the risk: it was material to her and she was entitled to know.


So it is important, following Montgomery, for experts to understand their role in giving evidence. They should confine their views to whether a doctor has correctly identified the reasonable range of treatment options and correctly assessed the medical risks and benefits (Role 1). Going beyond that to consider what should be discussed with the patient (Role 2) is not a matter of purely medical skill. It is a matter for the judge and experts should beware of trespassing on the judge's domain. 

You may also be interested in Paul Sankey's article, 'Patient consent and patient preferences'.


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