Capacity, refusal and substitute decisions

Marion's Case (1992): Limits to Parental Consent

In Secretary, Department of Health and Community Services v JWB and SMB (Marion's Case) (1992) 175 CLR 218, the High Court of Australia defined the strict boundaries of parental decision-making authority over children with intellectual disabilities.

• Case Background: Marion was a 14-year-old girl with severe intellectual disability, epilepsy, and behavioral issues. Her parents sought authorization to consent to a hysterectomy and bilateral oophorectomy to eliminate menstruation and prevent future pregnancy.

• The High Court's Ruling:

  • Parental authority does NOT extend to consenting to non-therapeutic, irreversible, highly invasive medical interventions that extinguish reproductive capability or permanently alter bodily integrity.
  • Such procedures are designated Special Medical Procedures.
  • Performing a non-therapeutic sterilisation without independent judicial authorization constitutes unlawful battery.
  • Special medical procedures: Non-therapeutic sterilisation of a minor falls outside ordinary parental authority and requires the appropriate court process. Do not assume every guardianship tribunal has jurisdiction over a minor; obtain specialist legal advice.

• Routine Pediatric Care: Decision-Making Authority: Parents / Legal Guardians; Legal Reference: Common law parental authority

• Mature Minor Seeking Contraception: Decision-Making Authority: The minor independently (if capable of full comprehension); Legal Reference: Gillick v West Norfolk (1986)

• Non-therapeutic Irreversible Sterilisation: Decision-Making Authority: Federal Circuit and Family Court of Australia or State Guardianship Tribunal; Legal Reference: Marion's Case (1992)

• Contested special treatment for a minor: Decision-Making Authority: Obtain current specialist and legal advice; parental agreement, the minor’s capacity and court requirements depend on treatment and jurisdiction; Legal Reference: Current law and the relevant court decisions

• Life-saving Emergency in an Unconscious Minor: Decision-Making Authority: Treating medical team (doctrine of emergency / necessity); Legal Reference: Australian common law emergency doctrine

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Assessing Mental Capacity: The Functional Approach

In Australian law, every adult is legally presumed to have decision-making capacity unless proven otherwise. Capacity cannot be determined solely on the basis of age, psychiatric diagnosis, cognitive disability, or whether a clinician agrees with the patient's choice.

Core Tenets of the Functional Framework

1. Decision-Specific: Capacity is not global. A patient with moderate dementia may lack the capacity to execute a complex estate will or consent to an elective coronary artery bypass graft, but may retain full capacity to consent to a routine influenza vaccination or blood test.
2. Time-Specific: Capacity fluctuates. In conditions such as delirium, acute intoxication, hypercapnia, or post-ictal confusion, capacity must be evaluated at the specific time the clinical decision is required. If a decision can safely be deferred until the acute metabolic or toxic state resolves, it should be postponed.
3. The Four-Part Functional Test: To possess capacity for a specific medical decision, the patient must be able to:
   • Understand: Comprehend the relevant clinical information regarding the illness, proposed treatment, realistic alternatives, and the consequences of refusing therapy.
   • Retain: Retain the relevant information long enough to deliberate and reach a decision.
   • Weigh: Process and weigh the risks, benefits, and trade-offs of the options in the balance.
   • Communicate: Express their choice clearly through speech, writing, signing, or augmented communication tools.

The Right to Make Unwise Decisions

A competent adult has the absolute right to make a medical decision that healthcare professionals, family members, or society regard as foolish, irrational, or contrary to their medical interests. An eccentric or unwise decision does not establish mental incapacity.

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Treatment Refusal, Advance Care Directives & Substitute Decision-Makers

The Absolute Right to Refuse Treatment

A competent adult has an absolute common law right to decline any medical therapy—including artificial nutrition, mechanical ventilation, renal dialysis, or life-saving blood products. When a competent adult makes an informed refusal, treating physicians must respect that refusal. Administering treatment over an informed, competent refusal constitutes medical battery and trespass to the person.

Jehovah's Witness Patients and Blood Products

A classic clinical scenario involves adult Jehovah's Witness patients who refuse blood transfusions:

• Adult refusal: Confirm decision-specific capacity, voluntariness and understanding, record the particular products/procedures declined or accepted, and respect an applicable informed refusal. A signature is useful evidence but is not the sole basis of valid refusal; beliefs differ between individuals.
• Clinicians must optimize all non-blood management options (e.g., tranexamic acid, cell salvage, high-dose erythropoietin, intravenous iron, desmopressin, and surgical hemostasis).
• Children and transfusion: Parents cannot refuse necessary lifesaving treatment merely because of their own beliefs. Use the local emergency statutory pathway or urgent court advice/order when needed. Mature-minor refusals also require careful legal assessment rather than assuming the adult refusal rule applies unchanged.

The Emergency Doctrine (Doctrine of Necessity)

When an adult patient is unconscious, delirious, or incompetent, and immediate clinical treatment is essential to save life or prevent serious, irreversible damage to health, clinicians are authorized under the common law doctrine of necessity to administer emergency medical treatment without consent. The emergency doctrine does not apply if clinicians are aware of an existing, legally valid advance refusal applicable to the emergency situation.

Advance care and substitute decisions

An advance directive may be statutory or recognised at common law; it is not always confined to a standard written form. Establish validity, applicability, revocation and the local statutory framework. A current capacitated decision takes precedence over an earlier plan. A valid applicable refusal is not erased merely because the patient becomes unconscious.

If capacity is absent, first check for an applicable directive and any appointed decision maker or tribunal guardian, including the scope of their authority. Default hierarchies vary. In NSW, a “person responsible” hierarchy differs from Victoria’s medical treatment decision maker scheme; an adult child is not automatically first in every state. Decisions should reflect the person’s known wishes and values, with the relevant statutory test when these are unknown.

If a substitute decision seems outside their authority or inconsistent with the legal standard, seek senior/legal or tribunal advice promptly. Emergency powers have defined conditions and do not automatically override a known valid refusal. Continue comfort care and communication regardless of whether a particular intervention is declined.

Primary references (checked 7 October 2026): Medical Board code.