Valid consent in Australia needs four things: capacity, voluntariness, adequate information and being specific to the treatment.
Capacity is decision-specific and presumed in adults. The patient must be able to:
- Understand the information.
- Retain it long enough to decide.
- Use and weigh it.
- Communicate a decision.
The key legal case is Rogers v Whitaker (1992): a doctor must warn of material risks, meaning risks a reasonable person would consider significant, or risks this particular patient would want to know about. A 1 in 14,000 risk of blindness was held to be material because the patient had asked about it.
A competent adult can refuse treatment, even if it leads to death. If a patient lacks capacity, look for an advance care directive, then a substitute decision-maker (guardian, enduring attorney or "person responsible", depending on the state). In an emergency, treat to save life or prevent serious harm.
Family consent is not automatic, unlike common practice in India.