39.1 Valid Consent and the Montgomery Standard

1. The Three Legal Pillars of Valid Consent

For consent to be legally valid and protect the clinician from civil liability or criminal charges of battery, three cumulative criteria must be satisfied:

The Three Cumulative Pillars of Valid Consent
  │
  ├── 1. Voluntary
  │     └── Decision made freely, without coercion, duress, or undue influence from family, carers, or clinicians
  │
  ├── 2. Informed
  │     └── Full disclosure of diagnosis, prognosis, treatment options, material risks, benefits, and costs
  │
  └── 3. Competent (Capacity)
        └── The patient possesses legal and mental capacity to make the specific decision at the material time

Consent as a Continuous Clinical Process

• Not a Static Form: A signed consent form is merely documentary evidence that a discussion took place; it does not prove that valid, informed consent was obtained. Consent is a continuous, dynamic dialogue.
• Right of Revocation: A patient with capacity possesses the unequivocal legal right to pause, reconsider, or revoke consent at any moment, including mid-procedure (e.g., signaling to stop during a restorative or surgical procedure).
• Express vs. Implied Consent:
  • Implied Consent: Non-verbal agreement for routine, non-invasive procedures (e.g., a patient opening their mouth and sitting back in the dental chair for a visual mirror examination).
  • Express Consent: Explicit verbal or written agreement required for any invasive, irreversible, or high-risk procedure (e.g., local anesthetic administration, tooth extraction, endodontics, crown preparation, or conscious sedation).

2. Landmark Ruling: Montgomery v Lanarkshire Health Board [2015]

The Supreme Court ruling in Montgomery v Lanarkshire Health Board [2015] UKSC 11 radically transformed the legal doctrine of consent across the United Kingdom, permanently discarding the paternalistic medical standard that had prevailed for decades.

Evolution of Consent Jurisprudence in UK Law

  1957: Bolam Test (Bolam v Friern Hospital Management Committee)
    └── Standard of care determined by a "responsible body of medical opinion"
    └── Applied historically to diagnosis, treatment, AND information disclosure

  1985: Sidaway Ruling (Sidaway v Board of Governors of the Bethlem Royal Hospital)
    └── Upheld Bolam for risk disclosure, except for "substantial risk of grave adverse consequences" (>10%)

  2015: Montgomery Supreme Court Landmark (Montgomery v Lanarkshire Health Board)
    └── Unanimously rejected the Bolam test for informed consent and risk disclosure
    └── Established Patient Autonomy: Doctors must disclose all "Material Risks"
    └── Defined dual test of materiality: Objective (Reasonable Person) & Subjective (Particular Patient)

The Historical Bolam Standard and Its Rejection

Under the Bolam test (Bolam v Friern Hospital Management Committee [1957]), a doctor was not deemed negligent if they acted in accordance with a practice accepted as proper by a responsible body of medical opinion. In Sidaway [1985], the House of Lords extended this principle to consent, allowing clinicians to withhold known surgical risks if a respected body of medical peers would also have withheld them.

In Montgomery [2015], the UK Supreme Court unanimously overturned this paternalistic approach, ruling that patients are consumers of healthcare who have the fundamental right to decide which risks they are willing to undergo.

The Legal Definition of a "Material Risk"

Under paragraph 87 of the Montgomery judgment, Lord Kerr and Lord Reed defined the legal standard:

$\mathbf{Material\ Risk\ Test}: \text{A risk is material if a reasonable person in the patient's position would attach significance to it,}$ $\mathbf{OR}\text{ the clinician is or should reasonably be aware that this particular patient would attach significance to it.}$

The Dual Branches of Materiality in Dental Practice

1. The Objective Branch (The Reasonable Person): Any risk that an average, reasonable individual undergoing that procedure would consider significant when deciding whether to proceed.
2. The Subjective Branch (The Particular Patient): A risk that might be statistically minor or uncommon, but holds profound, unique significance to that specific patient due to their profession, lifestyle, hobbies, or personal values.

[!IMPORTANT] The Therapeutic Exception: Under Montgomery, a doctor may withhold information regarding a risk only under two extremely narrow legal circumstances: (1) Emergency treatment where the patient is unconscious or incapacitated and urgent treatment is necessary to save life or prevent serious deterioration; or (2) Therapeutic Privilege, where the clinician reasonably believes that disclosure of the risk would cause serious physical or psychological harm to the patient (this does not include the patient becoming anxious or refusing treatment).

Consent in Everyday Dental Practice

The legal doctrine has to be turned into a routine. In UK dental practice, valid consent means the patient has capacity, has been given sufficient information, and is acting voluntarily, free from pressure from the clinician, from family or from financial inducement. The information must include the nature and purpose of the proposed treatment, its material risks and benefits, the reasonable alternatives including the option of doing nothing and their risks and benefits, who will carry out the treatment, and the cost, provided in writing before treatment begins.

Two practical rules follow. First, consent is a process, not a signature: a signed form is evidence that a conversation happened but is not itself consent, and a form signed without discussion is worthless. Second, consent must be specific: consent to an examination is not consent to an extraction, and consent given at a previous visit should be confirmed before an irreversible procedure begins. Where a plan changes mid-procedure, the correct action is to stop and obtain consent for the new plan unless there is an immediate risk to life — a favourite examination scenario in which "continue and explain afterwards" is the wrong answer.