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A Will is one of the most personal documents you’ll ever create. 

It names your executor, decides who inherits your assets, appoints guardians for children if needed, and reflects your wishes clearly. 

But life changes — relationships shift, health declines, accidents occur, dementia progresses — and sometimes the person who made the Will (or never made one) can no longer understand or update it. 

Families often assume it’s too late, but in South Australia, that’s not always the case.

The Succession Act 2023 (SA) (which commenced on 1 January 2025 and replaced the old Wills Act 1936 and related laws) provides clear pathways forward — both for people who still have some capacity and for those who have lost it entirely.

1. Testamentary Capacity: Can Someone with Dementia Still Make or Update a Will?

Even with a dementia diagnosis, capacity isn’t automatically lost. It can fluctuate, especially in early stages, and depends on the cause and progression of the condition.

To have testamentary capacity when giving instructions and executing the Will, a person must:

• Understand what they are doing and be able to give clear instructions
• Know the extent of their property and assets
• Be able to comprehend and appreciate who might reasonably expect to benefit (and why some might be excluded)
• Be free from any disorder of the mind (delusion or influence) that would distort their decisions about disposing of their property

Solicitors take this seriously. 

If there’s any doubt, we routinely recommend a medical assessment — ideally a detailed report from a neuropsychologist or geriatrician — outlining the person’s decision-making ability and whether dementia (or other conditions) affects their testamentary capacity. This evidence significantly reduces the risk of later challenges to the Will’s validity.

2. Statutory Wills: When Capacity Is Lost (or Never Existed)

If testamentary capacity is gone — or was never present — the Supreme Court can intervene under section 7 of the Succession Act 2023 (SA). The Court can:

• Make a new Will
• Alter an existing Will
• Revoke the whole or part of an existing Will

This applies even to minors or people who have never had capacity.

To make an order, the Court must be satisfied of two things:

1. The person lacks testamentary capacity
2. The proposed Will (or change) is one the person would make if they had capacity

Applications require leave (permission) first. 

The applicant (usually a close family member, enduring power of attorney, or Public Trustee) must provide:

• Medical evidence confirming incapacity
• Likelihood of regaining capacity
• Evidence of past wishes (previous Wills, conversations, letters)
• Current family and financial circumstances
• Draft proposed Will or changes
• Details of potential family provision claims, charitable intentions, or intestacy beneficiaries

The Court takes a practical, evidence-based approach, considering relationships, asset protection needs, family dynamics, and logical outcomes.

Real Australian Cases Showing How It Works

The Supreme Court in Queensland has approved statutory Wills in several cases, taking a common-sense view:

Matsis; Charalambous v Ors [2012] QSC 349  

A 90-year-old man with over $13 million in assets had a basic Will leaving everything to his late wife, then the family home to one grandson and the residue equally to three grandsons. After his wife’s death, dementia took hold and capacity was lost. Two grandsons were now running high-risk businesses — testamentary trusts would provide asset protection and tax benefits. One grandson applied for a codicil to include those trusts. No other changes were sought. The Court authorised it, satisfied this reflected what the man would have wanted if capable.

RKC v JNS [2014] QSC 313

A 12-year-old girl with severe cerebral palsy and profound intellectual disability received $1.375 million from a medical negligence claim after birth complications. She had no capacity and never would. Intestacy would split her estate equally between her parents — despite her father providing no support or involvement. Her mother applied for a statutory Will gifting to her and other family members, excluding the father. The Court approved it, finding it aligned with what the girl would likely have chosen.

ADT v LRT (No 2) [2014] QSC 188

A woman in the advanced stages of Alzheimer’s lacked capacity to change her Will, which left $5 million to her son amid his bitter divorce. The son argued his mother would want testamentary trusts to keep assets in the family. His estranged wife claimed the inheritance expectation had influenced family financial decisions. The Court authorised the trusts, satisfied this matched the mother’s probable intentions.

Doughan v Straguszu & Ors [2013] QSC 295

A daughter applied for her mother with dementia. The existing Will was unclear and failed to properly deal with assets like the family farm. A brother (also a beneficiary) faced bankruptcy risks. The proposed changes better protected the farm for future generations. The Court approved the variation, satisfied the timing was driven by sensible succession planning rather than solely the brother’s financial problems.

Additional Planning When Capacity May Be an Issue

If dementia or disability is diagnosed, it’s wise to review or create:

• Enduring Power of Attorney (financial/personal) — appoints someone to manage your affairs when you can’t
• Appointment of Medical Treatment Decision Maker — lets a trusted person make medical decisions if capacity is lost

Without these, families may need to apply to the South Australian Civil and Administrative Tribunal (SACAT) for guardianship/administration orders — which can be slower and more costly.

Key Takeaways

• Testamentary capacity can sometimes exist even with dementia — medical evidence helps confirm it.
• If capacity is lost, the Supreme Court can make or vary a Will under s 7 of the Succession Act 2023 (SA).
• Success depends on strong evidence of incapacity and likely wishes.
• Early planning (Powers of Attorney, medical decision-makers) avoids uncertainty later.

At Visual Legal, we help families prepare statutory Will applications, enduring appointments, and capacity assessments. If this situation sounds familiar — whether someone still has capacity or has lost it — book a free consultation. 

We’ll meet in our central Adelaide office or via secure teleconference, listen carefully, explain the process and prospects in plain terms, and guide you on the next steps. 

No pressure, just practical support.

Questions about Wills, capacity, or statutory options in South Australia? Drop them below or get in touch — we’re here to help.