Consent – Competent Adults


Consent is a fundamental principle in medical and health law. It includes the right to choose what treatment a person will undergo, and the right to refuse treatment that a person does not wish to have.

For consent to (or refusal of) treatment to be valid in a healthcare setting, the person must:

  • have legal competency and capacity to make a decision about treatment;
  • be informed of and understand the broad nature or character of the treatment and its effects;
  • give consent that relates specifically to the proposed treatment or intervention;
  • have made the decision regarding treatment voluntarily.

Note the principles discussed in this section relate to adults. There are special considerations to be had when a person is a ‘minor’ or lacks the capacity to consent due to their mental or physical state.

When are people considered adults in Australia?

In Australia, a person 18 years and over is legally considered to be an adult. 1

Types of Consent


A patient may consent to medical treatment by explicitly agreeing either orally or in writing to the treatment or intervention proposed.

Note: although great emphasis is placed on ‘consent forms’ in health settings, and consent forms may evidence a patient’s wishes, express consent does not need to be in writing. Further, the signing of a consent form is not be enough to show consent if there has been no explanation given of the procedure, or the other elements of consent are not present.

While it is good practice to document all conversations that occur regarding a person’s condition, this in itself is not the same as seeking express and valid consent.

Being clear on what a patient has expressly consented to, is important.

Consider the case of Ljubic v Armellin [2009] to further understand this point.


Implied consent refers to situations in which a person’s actions or words indicate that they consent, even though they may not expressly state that this is so. The common example given for this is when a person rolls up their sleeve and offers it to a doctor to have an immunization injection. Such action would imply that the person consents to the immunization.

Of course, it can be a little more complicated, as it is also sometimes difficult to discern what a patient is or is not consenting to, by implication. For example, attendance at a doctor’s rooms or hospital does not imply consent to all possible treatments. Holding ones arm out for immunization for measles, mumps and rubella, is not an implied consent to any type of injection.

Note also that implied consent does not justify treatment of someone who is temporarily or permanently incapacitated. There are special laws governing consent for incapacitated patients.

Elements of Consent

Legal Competence/Capacity

Capacity to consent at law has been taken to mean that a patient:

a) is able to comprehend and retain the information;

b) is able to believe it (in the sense that he/she is not ‘unable to reason’, or ‘divorced from reality’);


c) is able to weigh the information, balancing risks and needs, to arrive at a decision. 2

An adult is presumed to have the capacity to consent to or refuse medical treatment unless and until that presumption is proven to be incorrect. 3

State and territory guardianship legislation is relevant when determining when someone is taken to lack capacity – see further the section on incapacity.

NOTE: While capacity is a legal term, doctors are usually the primary assessors of that capacity regarding the particular decision to be made at the time when consent is sought.

Consent is specific to the treatment

The treatment provided must fall within the scope of the specific consent that has been given by the patient.

To satisfy that this is so, the patient must have been informed in broad terms of the nature of the proposed treatment. 4 The information provided should go to the essential character of the acts to be performed.

Note this is different to informing a patient of material risks and consequences of a procedure or treatment, which if not done, would found a cause of action in negligence.

An example of the scope and nature of consent being important is found in the case of Dean v Phung , in which a dentist who was found to be motivated by financial gain, carried out unnecessary dental treatment. Mr Dean’s consent was found to pertain only to necessary treatment, and not to the additional unnecessary work. As a result, the treatment constituted a trespass to the person.

Consider also the above-mentioned case of Ljubic v Armellin in which a woman was held to have consented to a hysterectomy, but not to the removal of her ovaries.

Consent must be voluntary

The final element of consent is that it must be given voluntarily and freely.
Consent will not be considered voluntary if it is
  • coerced
  • induced by fraud or deceit
  • induced by the impairment by drugs on the person’s faculty of reason
  • brought about by constraint on a person’s freedom of will, or
  • a product of the power relationship between the person who is ‘consenting’ (the patient) and the health professional. 5

The right to refuse treatment

Competent adults have a right to refuse treatment, even if the treatment would be life-saving.

There are several common law authorities that have stated the principle in terms of the rights and liberties of people to self-determination. 6

In Australia McHugh J, in the High Court case known as ‘Marion’s case’, said:

‘It is the central thesis of the common law doctrine of trespass of the person that the voluntary choices and decisions of an adult person of sound mind concerning what is or is not done to his or her body must be respected and accepted, irrespective of what others, including doctors, may think is in the best interests of that particular person…By doing so, the common law accepts that a person has rights of control and self-determination in respect of his or her body which other persons must respect.’ 7

The paramount consideration is that a person is entitled to make his own decisions about his life. 8

In addition to the common law, legislation in a number of states and territories recognises that a patient is entitled to refuse medical treatment. 9

Exceptions to the requirement for consent

There are some lawful exceptions to the requirement for consent, or the right to refuse treatment.

These include such things as:

  • the preservation of life (eg. in an emergency; following a suicide attempt)
  • self-defence (action may be taken to protect oneself)
  • defence of another person or property
  • statutory powers to treat and or detain in mental health settings; or to examine and detain in regard to infectious diseases.

Note that each case will be determined by its facts and the context in which the circumstances arose, and that any action taken without a person’s consent would have to be reasonable and proportionate to the circumstances.

Find out more


  1. Age of Majority Act 1977 (Vic) s3; Age of Majority (Reduction) Act 1971 (SA), s3; Age of Majority Act 1972 (WA), s5; Age of Majority Act (NT) s4; Law Reform Act 1995 (Qld), s17; Age of Majority Act 1974 (ACT) s5; Minors (Property and Contracts) Act 1970 (NSW), s9; Age of Majority Act 1973 (Tas), s3.
  2. Re C [1994] 1 WLR 290 and Re MB [1997] SCR 514 per LJ Butler-Sloss at 442. Re MB [1997] SCR 514 and Re T (Adult: Refusal of Treatment) [1993] Fam 95 (which concerned rationality as part of capacity) were approved in the Australian cases of Hunter and New England Area Health Service v A [2009] NSWSC 761 at 15, and Brightwater Care Group (Inc) v Rossiter [2009] WASC 229 at [27].
  3. Re MB [1997] SCR 514 at 513
  4. Rogers v Whitaker (1982) 175 CLR 479 at 490.
  5. Norberg v Wynrib (1992) 92 DLR 449 (Can SC) at 457, 468 (per La Forest J).
  6. See for example, Airedale NHS Trust v Bland [1993] AC 789 per Lord Keith at 857; Dept of Health and Community Services (NT) v JWB (‘Marion’s Case’) [1992] 175 CLR 218 at 309-310; Rogers v Whittaker (1992) 175 CLR 479.
  7. Dept of Health and Community Services (NT) v JWB (‘Marion’s Case’) [1992] 175 CLR 218 at 309-310.
  8. Rogers v Whittaker (1992) 175 CLR 479, citing F v R (1983) 33 SASR 189 (1983) per King CJ at 194.
  9. For example see Medical Treatment (Health Directions) Act 2006 (ACT) s 6, Medical Treatment Act 1998 (Vic) s 4, Consent to Medical Treatment and Palliative Care Act 1995 (SA) s7; Guardianship and Administration Act 1990 (WA).