Negligence is a failure to take reasonable care to avoid causing injury or loss to another person. There are four steps in proving negligence. The plaintiff must prove:

The standard of care for a health professional is that expected of the reasonably competent practitioner of that profession. The actions of the health professional will be compared with the standard. The court, not the professional, sets the standard, so even if a particular practice is common or accepted by other practitioners, it may still be negligent. Negligence can occur in any aspect of professional practice, whether history taking, advice, examination, testing or failing to test, reporting and acting on results of tests, or treatment. The standard is one of reasonable care, not of perfection. The court will decide having regard to all the circumstances whether the health professional has been negligent. Negligence is different from mistake or error of judgment. The fact that a risk of treatment eventuated, or that a desired medical outcome was not achieved, does not necessarily establish negligence.

A practical effect of this test is that if a person chooses to have (or through an emergency, is forced to have) a general practitioner perform surgery or administer general anaesthetic, then the person cannot expect the degree of skill of a specialist surgeon or anaesthetist. However, if the general practitioner holds himself or herself out as having special skill in surgery or anaesthetics, then the patient may be entitled to expect specialist skill.