Last updated 4 July 2016
Before a person can consent to or refuse particular medical treatment, they need to have a reasonable understanding of what that treatment involves. The treating health practitioner is required to provide a proper explanation of the medical treatment and the risks involved. A health professional has a duty to warn a patient of a material risk inherent in proposed treatment (see the High Court of Australia decision in Rogers v Whittaker (1992) 175 CLR 479;  HCA 58). A risk is evident if in the particular case:
- a reasonable person in the patient’s position, if warned of the risk, would be likely to attach significance to it
- the health practitioner is, or should reasonably be, aware that the particular patient, if warned of the risk, would be likely to attach significance to the risk.
Other factors relevant in deciding what information to provide and the recognition that this often depends on the circumstances are:
- the condition of the patient and their general health
- the nature of the medical treatment
- what will happen if the treatment fails or goes wrong
- how likely it is that a failure or particular risk may occur
- the seriousness of the effect on the patient’s health or life if a particular risk occurs
- whether the patient appears to want a full explanation of what is involved, the nature and the availability of alternative treatment
- the personality or temperament of the patient
- whether the treatment is needed because of an emergency (e.g. a car accident).
The law recognises that a health professional is justified in withholding information in certain circumstances. These include:
- reasonable grounds for believing that the physical or mental health of the patient might be seriously harmed by knowing particular information
- a patient does not wish to know all the information associated with their medical treatment. However, this does not mean the medical practitioner is not required to provide any information. In order for consent to be informed and valid, the patient must still be provided with enough information to enable them to properly consent
- the patient is unable to provide consent (e.g. the patient is unconscious). Treatment in this situation can only be provided if it is reasonably necessary in the best interests of the patient. When a person is unable to provide consent, consent can be provided by a person’s statutory health attorney (for more information see the chapter on Laws Relating to Individual Decision Making).
Types of consent
Where consent is provided to medical treatment by a person it must be freely given. The consent provided can either be:
- express—for example a person signs a form consenting to a particular surgical procedure or
- implied—for example, by the actions of the individual attending at a pathology centre, handing over the collection request form and presenting an arm for the blood test.
Consent and competent adults
There is a general presumption that an adult is competent to make medical decisions. A person who is 18 years of age or older and competent can consent or refuse to consent to medical treatment. A person making such a decision must be able to understand the relevant medical condition and the choices available in relation to the treatment of the condition. If consent to treatment is provided by a competent patient, the treatment provided is lawful. However, if the treatment is provided without consent, the relevant health practitioner or health service provider may be liable for assault or trespass. There are, of course, exceptions to the requirement for consent. For example, in cases of emergency or necessity, it may not be possible to obtain the consent of an individual to treatment. In those circumstances, the general position is that the provision of the treatment in the absence of consent will not constitute an assault or trespass to the person and therefore not attract civil or criminal liability.
Consent and children
A parent or guardian of a child generally has authority to consent or refuse medical treatment on behalf of their child. However, a child under 18 can make their own medical decisions where they have sufficient understanding and intelligence to fully understand the treatment (see Gillick v West Norfolk and Wisbech Area Health Authority  AC 112 and Secretary, Department of Health & Community Services (NT) v JWB and SMB (Marion’s Case) (1992) 175 CLR 218). A variety of factors can impact on any assessment of the capacity of a child to provide consent to medical treatment including their age, maturity and the seriousness (or not) of the medical condition. For further details on medical treatment and children see Parents, Children and the Law.