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№ 22 Wills & Estates

Can Someone With Dementia Still Change a Will in New Brunswick?

Can a loved one with dementia still sign or change a will? Learn how capacity is judged, how doubts are challenged and who can act in New Brunswick.

Wills & Estates4 min readTSLBy the Treadstone Law Team · New BrunswickUpdated November 13, 2026
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Key takeaways
  • A dementia diagnosis alone does not settle the question; capacity to make a will is tested against common-law principles in New Brunswick.
  • The person defending a will carries the burden on capacity and on knowledge and approval, while fraud or undue influence must be proved by those attacking it.
  • A will must also meet formalities, such as signature before two or more witnesses present at the same time.

When a parent or spouse has dementia, families often worry about whether a will signed or changed during that period will hold up. The worry goes both ways: some want to protect a person's wishes, others suspect those wishes were pushed.

This article explains the ideas courts use, what happens when a will is doubted, and what to gather if you are concerned. It does not decide any particular case, which depends on medical and other evidence.

This article covers the law of New Brunswick.

What testamentary capacity means

Testamentary capacity is the mental ability needed to make a valid will. The Wills Act does not set out the grounds for challenging a will based on capacity, undue influence, fraud or lack of knowledge and approval. These are decided by common-law principles, and the Probate Court follows common law principles absent a contrary provision.

Dementia is a spectrum, and a diagnosis does not by itself answer that question. A lawyer can explain how that evidence is weighed.

Who has to prove what

The Supreme Court of Canada, in Vout v. Hay, holds that the person propounding the will carries the burden on capacity and on knowledge and approval, and that burden shifts back if suspicious circumstances arise. Fraud or undue influence must be proved by those attacking the will. Simply being disappointed or excluded is not itself a ground.

IssueWho generally carries the burden
CapacityThe person propounding the will, shifting back if suspicious circumstances arise
Knowledge and approvalThe person propounding the will, shifting back if suspicious circumstances arise
FraudThose attacking the will
Undue influenceThose attacking the will

Formalities still count

Even where capacity is not in doubt, a will is valid only if signed at its end by the testator before two or more attesting witnesses present at the same time, who then sign in the testator's presence. Exceptions include holograph wills wholly in the testator's handwriting and signed, which need no witnesses. A court may also declare a document valid as a will if satisfied it embodies the deceased's testamentary intentions despite not meeting formal requirements.

A gift to an attesting witness or the witness's spouse is void as to that person, unless at least two other disinterested witnesses attested. Creditors and executors who witness are not disqualified.

How doubts are raised

A person who expects a challenge can lodge a caveat against a grant with the Registrar or a probate office clerk. It remains in force six months after lodging unless withdrawn, vacated or a notice of intent to contest is filed. The caveator must file a notice of intent to contest in Form 3D within ten days of receiving the warning.

The Probate Court may make interested persons parties to proof of a will in solemn form or to revocation proceedings. Instituting a contested claim or proof in solemn form costs $50, and a caveat or notice of intent to contest costs $25. A party served with a citation who does not file a notice of intent to contest is not entitled to notice of further proceedings.

Dependants have a separate route. A spouse, child or other dependant under the Family Law Act may ask a judge of the Court of King's Bench for support out of the estate, even against a will. The application must generally be made no later than four months after the death.

What to do next

Frequently asked questions

Does a dementia diagnosis make a will invalid?

Not automatically. Capacity and related challenges are decided by common-law principles, and the court looks at the evidence. A lawyer can tell you how a particular diagnosis might matter.

Who must prove capacity?

The person propounding the will carries the burden on capacity and on knowledge and approval, shifting back if suspicious circumstances arise. Fraud or undue influence must be proved by those attacking the will.

Is being left out of a will enough to challenge it?

No. Simply being disappointed or excluded is not itself a ground. If you were a dependant, a separate support application may be possible within four months of the death.

Can I stop probate while I look into it?

A caveat can be lodged against a grant, and no proceedings may be taken on the application without notice to the caveator. It lasts six months unless withdrawn, vacated or a notice of intent to contest is filed.

Sources

Links go to official government, court and regulator pages. The law changes — confirm you are reading the current version.

This article is general information, not legal advice. Reading it does not create a lawyer-client relationship. New Brunswick laws, tax rates, and government programs change, and how the law applies depends on your specific facts. For advice about your situation, speak with a lawyer who practises in New Brunswick. Reach us at 1-844-900-1070 or send our Team a message.

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