Decision Making Capacity Victoria: How It's Assessed and Why It Matters for Advance Directives

Capacity Is Presumed in Victoria — Until It Isn't

Under the Medical Treatment Planning and Decisions Act 2016, every adult in Victoria is presumed to have decision-making capacity. Nobody needs to prove they're competent before making medical decisions, executing an advance care directive, or appointing a Medical Treatment Decision Maker.

This presumption is important because it means capacity challenges must be substantiated — a family member can't simply assert that someone "isn't thinking clearly" and use that to block their planning documents. The burden falls on whoever disputes capacity to demonstrate that it's lacking.

But the presumption also creates a practical vulnerability. If you sign an advance care directive today and develop dementia two years from now, a family member could argue that you lacked capacity when you signed. Without a contemporaneous assessment on file, proving capacity retrospectively is difficult.

What "Decision-Making Capacity" Actually Means

Victorian law defines capacity in terms of four functional abilities. A person has capacity for a specific decision if they can:

1. Understand the information relevant to the decision and its effect.
2. Retain that information long enough to make the decision.
3. Use or weigh the information as part of the decision-making process.
4. Communicate the decision in some way (verbally, in writing, through gestures, or with communication aids).

Capacity is decision-specific. A person might have capacity to decide what to eat for lunch but lack capacity to understand the implications of refusing life-sustaining treatment. Each decision is assessed independently.

Capacity is also time-specific. Someone with early-stage dementia may have fluctuating capacity — lucid periods where they can make complex decisions and other periods where they cannot. The key question is whether they had capacity at the specific moment they signed the document.

When a Formal Assessment Matters

A formal capacity assessment isn't required to execute an ACD or MTDM appointment. Since capacity is presumed, most people can simply complete and sign the forms without any medical evaluation.

However, a formal assessment becomes important in three situations:

Early-stage cognitive impairment. If you've been diagnosed with dementia, mild cognitive impairment, acquired brain injury, or a psychiatric condition that affects cognition, a contemporaneous capacity assessment from your treating physician creates a documented record that protects your directive from later challenges. The assessment should note that you understood the nature of the directive, could weigh the treatment options, and communicated your decisions clearly.

Family conflict. If you anticipate that family members may disagree with your medical choices or challenge your directive's validity after you lose capacity, a formal assessment conducted at the time of signing is your strongest defence. Some people also have a solicitor present to provide an independent legal record.

Hospital-based assessments. When a patient is admitted and requires treatment, the treating medical practitioner must assess whether they have capacity to consent. If the patient lacks capacity, the practitioner searches for an ACD or MTDM. This clinical assessment is separate from any pre-existing documentation — it's a real-time evaluation of the patient's current state.

Who Performs the Assessment

Any registered medical practitioner can assess decision-making capacity in Victoria. In practice:

• Your GP handles most assessments related to advance care planning. They know your medical history and can contextualise the assessment against your baseline cognitive function.
• A geriatrician or neuropsychologist may be involved for complex cases, such as early-stage dementia where capacity is borderline.
• The treating team in a hospital setting performs real-time capacity assessments when a patient requires treatment.

There's no standardised form mandated by the Act for capacity assessments. Clinicians typically document their findings in the patient record, noting the specific decision being assessed, the questions asked, the patient's responses, and their clinical conclusion.

The Window for Advance Care Planning

This is the practical urgency behind capacity assessment. Conditions like Alzheimer's disease, vascular dementia, and frontotemporal dementia progressively erode decision-making capacity. There's a window — sometimes measured in months, sometimes in years — during which a person with an early diagnosis can still execute valid legal documents.

Once that window closes, the person can no longer create an ACD or appoint an MTDM. Their family is then left relying on the statutory decision-making hierarchy (spouse, then carer, then oldest child, then parent, then sibling) or applying to VCAT for a guardianship order. Neither option gives the person themselves any control over their future medical care.

Getting a formal capacity assessment during this window serves two purposes: it confirms the directive is valid, and it creates a dated clinical record that protects against future challenges.

Protecting Your Directive

A directive executed with a documented capacity assessment, witnessed by a GP who verified your understanding, and supported by clear instructional language is extremely difficult to challenge. The Victoria Advance Directive & Living Will Kit includes guidance on when and how to request a capacity assessment, what to discuss with your GP, and how to draft instructions that are clear enough to withstand scrutiny.

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