Put simply, the law accepts that the doctor may give analgesics (i.e. drugs which remove or relieve pain) that hasten the patient's death, and foresee that they will do so, but he or she must intend only to relieve pain, not to kill the patient, even if the patient has asked for help to die. This is known as the principle of double effect.
The principle of double effect has extended to include, since about 1988, the deliberate sedation of patients to deep unconsciousness for the purpose of relieving suffering. This is called terminal sedation because it can hasten death. more...
Medical Treatment Act
As per the Victorian Medical Treatment Act 1988, patients have the right to refuse medical treatment and this may, as a result, cause their death ("Passive Euthanasia").
Refusal of Treatment forms are available here.
This Victorian Medical Treatment Act was amended in 1990 and 1992 to allow a person to appoint an agent to act on his or her behalf, if (and only if) he or she should become incompetent. The form to appoint an agent ("Enduring Power of Attorney") and more information on this are available here.