Key Takeaways
- Testamentary capacity means the legal and mental ability to make a valid Will.
- The test comes from Banks v Goodfellow and focuses on whether the Will-maker understood the Will, their assets, and the people who may have moral claims to their estate.
- The Will-maker must have testamentary capacity when giving instructions and executing their Will.
- Dementia or cognitive decline does not automatically invalidate a Will or mean the Will-maker lacked testamentary capacity.
- If testamentary capacity is successfully challenged, the Will may be declared invalid and an earlier Will or intestacy rules may apply.
Sometimes a Will raises more questions than it answers.
A parent changes their wishes late in life. A long-standing beneficiary is removed. A new person receives far more than expected. A Will is signed in hospital, in aged care, or after months of visible decline.
Families are then left asking the hardest question of all: did they really understand what they were doing?
In Western Australia, that question can decide whether a Will stands or falls. It’s also one of the most sensitive issues in inheritance law, because it sits where grief, memory, medicine and family conflict meet.
What is testamentary capacity?
Testamentary capacity refers to a person’s legal and mental ability to make a valid Will.
In a Will dispute, the question is whether the Will-maker had sufficient understanding to make decisions about their estate at the time the Will was made. This includes whether they understood the nature of the Will, the extent of their assets, and the family members or others who have or may later have moral claims against their estate.
Capacity is decision-specific. A person may have capacity to make legal decisions for themselves, but can lack testamentary capacity when making a Will. In Will disputes, the focus is whether the Will-maker had the required understanding when the Will was made.
That’s why testamentary capacity is assessed carefully. The focus is not whether the Will seems fair. The focus is whether the Will-maker understood what they were doing, who they were affecting, and the consequences of the choices they made.
The Banks v Goodfellow test
The legal test for testamentary capacity comes from the case of Banks v Goodfellow. Although the case dates back to 1870, it remains the foundation for determining testamentary capacity in Australian Will disputes today.
The four key questions are set out below.
1. Did the Will-maker understand the nature of making a Will?
The person must understand that they are making a Will and that the document will decide what happens to their estate after death.
They don’t need to understand every legal phrase in the document. But they do need to understand the nature and effect of the document.
2. Did they understand the extent of their assets?
The Will-maker must have a general understanding of the extent of their assets.
This doesn’t mean they need to know the exact value of every bank account, property, shareholding or personal item. But they should understand, in broad terms, what they own, what falls into their estate, and what they are giving away.
This can become more complex where the estate involves family trusts, business interests, superannuation, rural properties, blended family arrangements or assets held in different names. Sometimes a deeper understanding can be required.
3. Did they understand who may have moral claims on their estate?
The Will-maker must understand the people who might reasonably expect to benefit from their estate.
This usually includes close family members, dependants and others with a strong claim on the Will-maker for responsibility or support.
This doesn’t mean every family member must receive something. A person can choose to exclude someone from their Will. But they must be able to understand who they are excluding, why that decision matters, and the likely consequences of that.
4. Were they free from any disorder of the mind that distorted their judgment?
The Will-maker must not be affected by a disorder of the mind that distorts the way they make decisions about their estate.
A dementia diagnosis, mental health condition or cognitive impairment doesn’t automatically mean the person lacks capacity. What matters is whether the condition interfered with their ability to make rational decisions about their Will.
For example, a Will may be challenged where the deceased held a fixed false belief about a family member, and that belief directly shaped who they chose to include or exclude.
The focus is on the connection between the condition and the Will itself. A medical diagnosis alone isn’t enough.
When does testamentary capacity need to exist?
Testamentary capacity is assessed at the time the Will is made. Put simply, capacity must exist when the Will-maker gives instructions and when they sign the final document.
That timing matters. A person may have lacked capacity beforehand, then recovered enough to make a valid Will. Equally, a person may seem capable in ordinary conversation, but lack capacity when giving instructions or signing the Will.
This is especially important where capacity fluctuates. A person’s understanding can change due to:
- dementia or cognitive decline;
- medication;
- infection;
- fatigue;
- grief;
- Hospitalisation; or
- serious illness.
The court looks closely at the Will-maker’s capacity when the key decisions were made. Their age, health and general presentation may be relevant, but not the final answer.
That’s why evidence around the date of the Will is so important. This may include medical records, solicitor file notes, witness evidence and observations from family members or carers. Evidence from weeks or months before or after may be helpful, but the closer to the signing, the more useful it may be.
Dementia, cognitive decline and lucid intervals
Dementia or cognitive decline doesn’t automatically mean a person lacked testamentary capacity.
A Will-maker may still be able to make a valid Will if they can understand the matters required by the Banks v Goodfellow test. This may be possible during a lucid interval, where the person has enough clarity to understand the decision they are making.
For families, the key point is simple. Dementia may raise a warning sign, but it does not answer the capacity question on its own.
How testamentary capacity is assessed before signing
When a person makes or changes a Will, the lawyer taking instructions has an important role in assessing testamentary capacity.
It’s a legal assessment based on whether the Will-maker understands the decision they’re making. Where there are concerns, a doctor or specialist may also be asked to assess the patient’s testamentary capacity and provide written evidence before finalising the Will.
A careful assessment usually involves the following steps.
1. Taking instructions directly from the Will-maker
The instructions should come from the person making the Will, not from a family member, carer or intended beneficiary.
It’s common for an adult child or trusted person to help arrange the appointment. But the final instructions must come from the Will-maker themselves.
Where possible, the lawyer should speak with the Will-maker alone. This helps confirm that the instructions are their own and that no one else is steering the outcome.
2. Asking questions that test the Banks v Goodfellow criteria
The lawyer should ask questions that help determine whether the Will-maker understands:
- what a Will is and what it does;
- the nature and extent of their assets;
- who may expect to benefit from their estate;
- why they are including or excluding certain people; and
- whether any illness, belief or confusion may be affecting their judgment.
These questions should be practical. A person may be able to say they want to make a Will, but still struggle to explain what they own, who their family members are, or why they are making significant changes.
3. Identifying whether extra safeguards are needed
The lawyer should consider whether the circumstances call for extra care before the Will is signed.
This may be the case where there is:
- recent cognitive decline;
- serious illness or hospitalisation;
- a major change from an earlier Will;
- a beneficiary arranging the appointment; or
- uncertainty about whether the Will-maker is giving their own instructions.
These factors don’t prove lack of capacity. They simply signal that the process should be managed and documented more carefully.
4. Keeping detailed file notes
Good file notes can become critical if the Will is later challenged.
A lawyer’s notes may record what questions were asked, how the Will-maker responded, who was present, whether the Will-maker appeared to understand the document, and why the lawyer was satisfied capacity existed.
Where there is a later dispute, those notes can be powerful evidence of what happened at the time and if any concerns about capacity were addressed and resolved.
5. Getting medical evidence where appropriate
If there are real concerns, the lawyer may recommend a medical assessment before the Will is signed.
This may involve a GP, geriatrician, psychiatrist or other suitably qualified medical practitioner. In some cases, a mini mental state examination may be used as part of a broader assessment. But it should not be treated as the whole answer. Testamentary capacity is a legal test, and the medical opinion needs to address the Will-maker’s understanding of the Will, their assets, and the claims of people who may expect to benefit.
The stronger the concern, the more important it is to create a clear record before signing. This can help protect the Will-maker’s wishes and reduce the risk of a later dispute.
For broader planning steps, read our guide on key strategies for protecting your Will from challenges.
How testamentary capacity is challenged after death
After death, testamentary capacity is usually challenged by someone who says the Will-maker lacked capacity when the Will was made.
The person challenging it will usually look for evidence showing the deceased did not understand what they were doing, what they owned, or who had moral claims on their estate.
That evidence may include:
- medical records;
- GP notes;
- hospital records;
- aged care records;
- solicitor file notes;
- earlier Wills;
- correspondence about the Will;
- witness evidence from family members, carers or friends; or
- expert medical or psychiatric evidence.
If you’re considering a challenge, our guide on what evidence you need to contest a Will in WA explains how evidence can shape the strength of a claim.
The solicitor’s file is often important. It may show how instructions were taken, who was present, what questions were asked, and whether the Will-maker appeared to understand the document.
Medical evidence can also be central, especially where the deceased patient had dementia, delirium, psychiatric illness, medication changes or other conditions affecting mental capacity.
In many disputes, the real question is whether the Will-maker understood their decision at the relevant time. A strange or unfair-looking Will may raise suspicion, but suspicion alone is not enough. The challenge needs evidence.
Testamentary capacity is only one reason a Will may be challenged. You can also read our broader guide on what can make a Will invalid.
12 commons pitfalls to avoid in protecting yourself, your loved ones, and your legacy.
Testamentary capacity, undue influence and coercion: What’s the difference?
Testamentary capacity is often raised alongside undue influence or coercion, but it’s important to highlight that they’re not the same thing.
A person may have mental capacity and still be pressured into making a Will that doesn’t reflect their true wishes. Equally, a person may not have been pressured by anyone, but may still lack capacity because they didn’t understand the decision they were making.
| Issue | What it focuses on | Common signs |
| Testamentary capacity | Whether the Will-maker had the mental capacity to understand the Will, their assets, and the moral claims of others | Dementia, confusion, inconsistent instructions, poor understanding of assets, inability to explain decisions |
| Undue influence | Whether another person overpowered the Will-maker’s free judgment | Isolation, dependency, pressure from a family member or carer, sudden changes benefiting one person |
| Coercion | Whether pressure, threats or control caused the Will-maker to act against their true wishes | Fear, intimidation, threats, controlling behaviour, the same person managing appointments or communication |
The difference matters because each issue is supported by different types of evidence.
A testamentary capacity dispute often relies heavily on medical records, solicitor file notes and evidence about the Will-maker’s understanding. An undue influence or coercion claim usually looks more closely at behaviour, relationships, control, dependency and the circumstances around the Will being made.
In some matters, both issues arise together. For example, an elderly Will-maker with declining mental capacity may become dependent on one family member, who then becomes heavily involved in arranging a new Will. That doesn’t automatically prove anything. But it may be enough to justify a closer look.
Red flags that may point to capacity or influence concerns
Concerns about testamentary capacity often arise because something about the Will feels out of step with what the family understood.
Sometimes the concern is mental capacity. Sometimes it’s pressure, control or undue influence. Often, families are not sure which issue applies until the circumstances are properly reviewed.
One red flag on its own may not be enough to challenge a Will. But several together can point to a deeper issue.
Common warning signs include:
- a Will made or changed very late in life;
- sudden changes that favour one person disproportionately;
- exclusion of a previously close family member;
- a new beneficiary appearing after a short or intense relationship;
- a Will made in hospital, aged care or during a serious medical episode;
- the Will-maker becoming isolated from long-standing family, friends or adviser;s;
- one person controlling appointments, transport, communication or access
- a family member, carer or beneficiary choosing the solicitor;
- the same person being present at every legal or medical appointment;
- instructions that seem inconsistent with earlier Wills or long-held intentions;
- the Will-maker appearing confused, fearful, dependent or unusually secretive; or
- unexplained hostility towards a family member based on beliefs that seem irrational or untrue.
Our research has identified late-life Wills and capacity concerns as a recurring source of estate disputes, particularly where a Will appears to favour one person who has become a gatekeeper to an elderly Will-maker.
These signs don’t prove lack of capacity by themselves. But they do suggest the Will, the surrounding circumstances and the evidence should be looked at carefully before assumptions become fixed positions.
What happens if a Will-maker lacked testamentary capacity?
If a Will-maker lacked testamentary capacity when the Will was made, the Will may be declared invalid.
What happens next depends on the circumstances.
The court may:
- uphold an earlier valid Will, if one exists;
- declare only part of the later Will invalid, if the issue affects only part of the document; or
- treat the estate as intestate, if there is no earlier valid Will.
Intestacy means the person has died without a valid Will. In Western Australia, the estate is then distributed under a fixed legal formula, rather than according to the person’s wishes. For more on how intestacy works in WA, read our guide to intestacy and why the law may not suit modern families.
This can create outcomes no one expected. A person the deceased intended to benefit may receive nothing. A family member they deliberately excluded may receive a share. The Executor named in the invalid Will may also lose their role.
That’s why testamentary capacity matters on both sides. For Will-makers, it helps protect their wishes. For families and beneficiaries, it can determine whether the Will should stand, or whether the estate needs to be dealt with another way.
What to do if you’re concerned about testamentary capacity
If you’re concerned about testamentary capacity, get advice early. The right steps depend on whether the Will-maker is still alive or the Will is already being questioned after death.
If the Will-maker is still alive
The priority is to protect their independence and create a clear record of their wishes.
- make sure instructions come directly from them;
- keep beneficiaries out of the appointment room;
- use an experienced estate planning lawyer;
- consider a medical capacity assessment if there are concerns;
- keep clear records of the Will-maker’s instructions and reasons; and
- avoid last-minute changes unless they’re properly explained and documented.
If the Will-maker has passed away
The priority is to preserve evidence and avoid steps that could make the dispute harder to resolve.
- do not assume the Will is valid or invalid without advice;
- gather earlier Wills, medical records, correspondence and solicitor details;
- write down what you observed around the time the Will was made;
- avoid distributing the estate until concerns are properly considered; and
- seek legal advice before contacting other beneficiaries or making allegations.
Why early conversations matter
In our 2026/2027 Inheritance State of Play Report, we found that 48% of respondents had not had a meaningful family conversation about estate planning. That silence can make testamentary capacity disputes harder, because families are left trying to piece together intention, context and evidence after the person has died.
Where capacity is in doubt, delay can make things harder. Records can be lost, memories can fade, and estates can be distributed before the issue is properly understood.
Get clear advice before the dispute hardens
When testamentary capacity is in doubt, clarity matters.
At Solomon Hollett Lawyers, our inheritance lawyers in Perth help families understand where they stand before decisions are made, estates are distributed, or disputes become harder to resolve. Where required, we can also support Testamentary Trusts in your Will to protect the people you love most.
We can help you assess whether there are genuine grounds to question testamentary capacity, or whether a Will should be protected and defended. We’ll look at the facts, the evidence and the legal pathway with care.
Book a free 15-minute phone call with our team and get clear, early guidance on whether your situation needs legal help.
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