Capacity and Various Legal Decisions

Capacity and Various Legal Decisions

Health Decisions

For information on health care decision making, go to Health Decisions – Overview


A contract is an agreement, usually between two people, which a court can enforce. Some contracts are in writing, but many are not.

If a person is suffering from such a degree of mental illness at the time of making a contract that they are not capable of understanding the nature of the contract, the contract may still be binding and may still be enforced by a court. However, the contract is voidable, which means that a court will not enforce the contract against the mentally ill person, if they (or someone acting on their behalf) can prove that the mental disability was known or should have been known to the other party.

When a mentally ill person purchases necessaries, the contract cannot be avoided just because the buyer is not mentally competent. Necessaries are goods suitable to the condition of the life of the person buying them and to their actual requirements at the time of the sale and delivery.

Section 5 of the Sale of Goods Act 1896 (Qld) provides that ‘… when necessaries are sold and delivered … to a person who by reason of mental incapacity … is incompetent to contract, the person must pay a reasonable price [for them] …’.


A person who has a mental illness and retains an understanding of the nature of voting is entitled to vote.

To enforce a voting right, it could be necessary to obtain an opinion from a qualified person about the mental capacity of the patient seeking to vote.

The State Electoral Office will strike someone off the electoral roll if it has received a notice from the patient’s relative, a doctor or the Public Trustee about the patient’s mental illness.


Section 23 of the Marriage Act 1961 (Cth) provides that a marriage is void if either party was mentally incapable of understanding the nature and effect of the marriage ceremony.

Provided a patient’s mental illness does not affect that capacity, a patient over the age of 18 can marry without seeking anyone’s consent.


There is no prohibition on a mentally ill person making a will, as long as that person has a testamentary capacity and the person can understand:
  • the will and its effects
  • the extent of the property involved
  • the claims of dependants or other family members for whom some provision should be considered.
However, sometimes the presence of delusions will affect a mentally ill person’s capacity to make a will.

The Supreme Court has power to authorise a will to be made (statutory will), altered or revoked for a person without testamentary capacity (s 21 Succession Act 1981 (Qld)).

Property and Personal Matters

Management of the property of a mentally ill person is not regulated by the Mental Health Act.

The Guardianship and Administration Act 2000 (Qld) (Guardianship and Administration Act) provides for the appointment of guardians to manage the personal affairs of adults with impaired capacity and for administrators to manage their financial affairs where necessary.

The Queensland Civil and Administrative Tribunal is responsible for appointing guardians and administrators to review such appointments and decide the matters on which guardians and administrators may make decisions for an adult with impaired capacity.

Together with the Powers of Attorney Act 1998 (Qld), the Guardianship and Administration Act provides a comprehensive scheme to facilitate the exercise of power for financial matters and personal matters by or for an adult who needs, or may need, another person to do those things for them.

ReferenceLaw Handbook

Can’t find what you’re looking for?