Undue Influence vs Lack of Testamentary Capacity: What's the Difference?

Why These Concepts Are Often Confused

Capacity and undue influence are routinely conflated by families, and sometimes even in early correspondence between lawyers. The reason is practical: the same fact pattern often triggers both concerns. An elderly parent with declining health signs a new Will heavily favouring one child, in circumstances where another child had less contact with the parent. Some family members assume the problem must be capacity; others assume the problem must be pressure from the favoured child. The honest answer is usually that both questions deserve consideration.

Capacity and influence also share many of the warning signs — sudden departures from a long-standing pattern, isolation of the Will-maker, a new beneficiary appearing late in life, or changes made during a period of illness. Pulling the two issues apart is one of the first tasks for a lawyer assessing a potential challenge.

What Is Testamentary Capacity?

Testamentary capacity is the legal test for whether a person is mentally capable of making a valid Will. The modern test traces back to Banks v Goodfellow (1870) and continues to be applied in Victoria. The Will-maker must understand the nature and effect of a Will, the general extent of their property, the people who might reasonably expect to benefit, and must be free from any disorder of the mind that distorts their decisions.

Capacity is assessed at the moment the Will is signed. It can fluctuate, and it can exist for simple Wills while being absent for complex ones. For a fuller overview, see our article on testamentary capacity in Victoria.

What Is Undue Influence?

Undue influence in the context of a Will means coercion — pressure on the Will-maker that is strong enough to overbear their free will. The classic phrase used by the Courts is that the Will reflects the wishes of the person applying the pressure rather than the wishes of the Will-maker themselves. The bar is deliberately high.

Importantly, undue influence is not the same as persuasion, advice or even strong family pressure. Encouraging a parent to revisit their estate plan, providing care that prompts a parent to be more generous, or asking a parent to reconsider an unfair Will is not, by itself, undue influence. The Court requires evidence that the Will-maker was effectively forced to make decisions they would not otherwise have made.

Because direct evidence of coercion is rare — coercion typically happens in private — undue influence cases usually depend on a combination of opportunity, vulnerability, the conduct of the alleged influencer and the terms of the Will itself.

Key Differences Between Capacity and Influence

The two issues are best understood by comparing them directly:

Can Both Issues Exist at the Same Time?

Yes — and they frequently do. Reduced cognition makes a person more vulnerable to influence, and the presence of a controlling family member or carer can both encourage a change of Will and obscure cognitive decline from outsiders. It is common for the same proceeding to plead lack of capacity and undue influence in the alternative.

For example, an elderly parent with early dementia may move in with one adult child after the death of a spouse. Over the following months, the parent becomes increasingly dependent on that child, has less contact with siblings, and is taken to a new solicitor who has never met the family before. A fresh Will is signed leaving the bulk of the estate to that child. After the parent's death the other siblings raise concerns. On those facts both issues — capacity and influence — warrant examination.

What Evidence Is Commonly Considered?

Both types of dispute are decided on the available evidence, much of which must be reconstructed after the Will-maker has died. The following categories are routinely relevant:

• Medical evidence — GP records, hospital admissions, specialist assessments and any neuropsychological reports relevant to cognition and vulnerability around the time the Will was signed.
• Solicitor file notes — the notes of the solicitor who prepared the Will, including the instructions received, the questions asked, who else was present and any capacity or undue-influence screening that took place.
• Witness evidence — statements from family members, friends, carers, neighbours and others who observed the Will-maker's behaviour, conversations and apparent independence at the relevant time.
• Family and social circumstances — living arrangements, who provided care, who had control of finances or correspondence, who arranged the solicitor's appointment, and whether the Will-maker had independent contact with other relatives.
• The Will and earlier Wills — the terms of the disputed Will, how dramatically it departs from earlier patterns, and whether the change can be explained on the evidence.

Why Medical Evidence May Matter

In both capacity and undue influence disputes, medical evidence often plays a central role. In capacity claims it speaks to whether the Will-maker met the legal test. In undue influence claims it speaks to vulnerability — the Will-maker's susceptibility to pressure at the relevant time.

Contemporaneous medical records, particularly those made by a GP or specialist who knew the Will-maker, can be decisive when combined with the solicitor's file and independent witness evidence. Where there are concerns about a person with dementia make a valid Will, medical records are typically the starting point.

Practical Warning Signs

The following situations commonly prompt concerns about either capacity, influence or both, and warrant a closer look:

• A new Will made shortly after a significant cognitive event, hospital admission or serious illness.
• A sudden departure from a long-standing testamentary pattern, particularly excluding children or grandchildren.
• A beneficiary arranging the solicitor's appointment, attending the meeting or providing instructions on the Will-maker's behalf.
• Isolation of the Will-maker from other family members, including restricted phone or visiting access.
• A new carer, friend or partner appearing late in life and becoming a significant beneficiary in a short period.
• Use of an unfamiliar solicitor with no prior knowledge of the family or estate.
• Wills made during hospitalisation, in palliative care or very close to death, particularly where the terms have changed dramatically.

None of these factors is decisive on its own. They are warning signs that warrant further inquiry into how the Will came to be made.

Practical Steps When Concerns Arise

Where there are concerns that a Will may have been made without capacity or under undue influence, the following steps can help protect the interests of beneficiaries and the Will-maker:

1. Act early — concerns should be raised and assessed as soon as they arise, ideally before probate is granted.
2. Identify medical evidence — make a list of GPs, specialists, hospitals and aged-care facilities that may hold relevant records, together with the approximate dates.
3. Identify witnesses — note who saw the Will-maker around the time the Will was signed, who was involved in arranging the appointment and who attended the meeting.
4. Preserve documents — earlier Wills, correspondence with the solicitor who prepared the disputed Will and any notes made by family members can all be relevant.
5. Avoid confrontation — direct accusations between family members can escalate the dispute and reduce the prospects of negotiated resolution.
6. Consider mediation — many estate disputes resolve through mediation without a final hearing.
7. Get early legal advice — capacity and undue influence challenges are evidence-heavy. An experienced estate disputes lawyer can assess the strength of the material before any formal step is taken. For broader context on a challenging a Will, see our companion article. These issues also intersect with Wills and estate planning advice for the next generation.

Conclusion

Lack of testamentary capacity and undue influence are distinct legal concepts that often present together in Victorian estate disputes. Capacity asks whether the Will-maker understood what they were doing. Undue influence asks whether someone else's coercion replaced the Will-maker's free decision. Both are decided on the evidence available after death, and both depend heavily on contemporaneous records and credible witnesses.

Where there are real concerns about how a Will came to be made, early legal advice is almost always the safest path. A clear assessment of the strength of the available evidence — medical, solicitor and witness — gives families a realistic basis on which to decide whether to negotiate, mediate or contest.

Frequently Asked Questions