In family law, legal capacity is essential for making decisions about children, entering into contracts, and giving evidence in court. Without this capacity, people may be unable to protect their own interests or the interests of their children. There are several factors that can affect a person’s legal capacity, including:
- Age
- Mental health or mental capacity
- Intellectual disability
In New South Wales, if there is a question about whether a person has legal capacity, an individual can use the “Capacity Toolkit.” The Capacity Toolkit is a manual for determining a person’s ability to make decisions on their legal, medical, financial, and personal affairs.
Moreover, it was developed in response to requests for more information regarding capacity, some general capacity principles, and instructions on evaluating a person’s capacity to make decisions from attorneys, medical professionals, health workers, carers, and advocates.
In family law, legal capacity pertains to the capacity of a person to make decisions about things that affect their daily life, such as matters that have legal consequences, including:
- making a Will
- getting married
- decisions about their children
- entering into contracts or agreements.
The legal capacity maze can be a difficult one to navigate. But with the help of an attorney, people with an impaired capacity can still make informed decisions about their lives and their children’s lives.
Why Legal Capacity Is Important in Family Law
Legal capacity is crucial in marriage, matters related to children, making a Will, and entering into agreements under family law because it ensures that people who are making decisions about these critical matters can understand the consequences of their actions.
In marriage, both parties must have the capacity for the marriage to be valid. This means that they must be able to understand the nature of the marriage contract and the rights and responsibilities that come with it. If one party lacks capacity, the marriage may be considered void.
For children, capacity is crucial because it determines who can make decisions about their upbringing. In most cases, parents have the capacity to make decisions about their children’s education, medical care, and other aspects of their lives. However, if a parent lacks capacity, the court may appoint legal guardians or other person to decide on their behalf.
A Will is a legal document that outlines a person’s wishes for their property after they die. For a Will to be valid, the person who makes it must have the testamentary capacity. This means that they must be able to understand the terms of the Will and the consequences of their actions.
Finally, capacity is also important when entering into agreements under family law. For example, if two people enter into a prenuptial agreement, they must both have the capacity in order for the agreement to be enforceable. This means that they must be able to understand the terms of the agreement and the consequences of their actions.

Factors That Can Affect a Person’s Legal Capacity
Under Australian law, a person’s capacity is their ability to make decisions about their own life. This includes decisions about their health, finances, and other important matters. There are a number of factors that can affect a person’s capacity, including:
- Mental illness. Some mental illnesses, such as dementia, schizophrenia, and severe depression, can negatively affect a person’s ability to make decisions. The Mental Health Act 2014 (VIC) also outlines a specific test for (and presumption of) capacity to provide informed consent to treatment.
- Physical illness. Physical illnesses, such as brain injuries, strokes, and Alzheimer’s disease, can also impair a person’s decision-making ability.
- Intellectual disability. People with intellectual disabilities may have difficulty understanding complex information or making complex decisions.
- Age. As people age, their mental and physical faculties may decline, which can have a negative impact on their capacity.
- Drugs and alcohol. The use of drugs and alcohol can impair a person’s ability to make decisions.
- Environmental factors. Stress, isolation, and other environmental factors can also affect a person’s capacity.
Legal Implications of Lacking Legal Capacity
If a person is found to lack capacity in Australia, they may be unable to make decisions about their own life. This can have a number of legal implications, including:
- They may not be able to enter into contracts with other people, such as contracts for goods or services.
- They may not be able to make decisions about their health, so they cannot consent to medical treatment or make decisions about their end-of-life care.
- They may not be able to manage their finances.
- They may not be able to vote. This means that they cannot vote in elections or referendums.
If a person lacks capacity, they may be appointed a guardian or administrator to make decisions on their behalf. The guardian or administrator will have the legal authority to make decisions about the person’s health, finances, and other matters.
The legal implications of lacking capacity can be significant. If you are concerned that a person may lack legal capacity, you should speak to a lawyer or other qualified professional.

Speak to a Family Lawyer Today
Family lawyers specialise in providing services to people who lack legal capacity. JB Solicitors’ family lawyers can help you with a range of tasks, including:
- Assessing capacity. If you are concerned that a person may lack capacity, a lawyer can assess their capacity and advise you on the next steps.
- Preparing and registering enduring powers of attorney. An enduring power of attorney is a legal document that allows you to appoint someone to make decisions on your own behalf if you lose your capacity. A lawyer can help you prepare and register an enduring power of attorney.
- Appointing a guardian or administrator. If a person is found to lack capacity, a court may appoint a guardian or administrator to make decisions on their behalf. A lawyer can help you appoint a guardian or administrator.
- Advocating for the person’s interests. If you are concerned about the person’s interests, a lawyer can advocate for them in court or other settings.
Send us an enquiry today if you need supported decision making for your legal matters.