Your parent was forgetting names. Getting confused about dates. Maybe they stopped recognizing the grandchildren they used to dote on. And then, months into that decline, they signed a new will — one that cuts you out entirely, or leaves almost everything to a new partner or a caregiver who moved in last year.
You want answers. Was that will even valid? Did your parent really understand what they were signing?
These are exactly the right questions to ask. But before you go further, you need to understand something that surprises most people who come to us with this situation: a dementia diagnosis, on its own, is not enough to void a will in BC.
Here's what the law actually requires — and what evidence can make or break a challenge.
What Is Testamentary Capacity?
"Testamentary capacity" is the legal term for the mental ability a person needs to make a valid will. BC courts still apply the classic test from the 1870 English case Banks v. Goodfellow, which has been consistently followed in British Columbia ever since.
To have testamentary capacity, a person must understand:
- The nature and effect of making a will — that they are creating a document that distributes their property after death.
- The extent of their property — a general sense of what they own. Not a precise inventory, but a reasonable awareness of their assets.
- The natural claims on their estate — who the people are that might reasonably expect to benefit, such as a spouse, children, or dependants.
- How those elements fit together — that they can hold all of this in mind at the same time and form an orderly plan.
Notice what's not on that list. A person doesn't need to remember what year it is. They don't need to pass a memory test. They don't need to recognize every grandchild by name. The test is narrower than most families expect, and courts apply it strictly.
This means someone with early-stage dementia can still have testamentary capacity — and a will they signed can be legally valid — even if that person was noticeably forgetful or confused in day-to-day life.
Why a Diagnosis Alone Won't Win Your Case
In Vail v. Vail, 2009 BCCA 98, the BC Court of Appeal addressed this directly. The court confirmed that a diagnosis of early dementia does not automatically prove lack of testamentary capacity. What matters is the person's cognitive state at the specific time the will was signed — not before, not after, but at that moment.
This is called the "golden rule" in will-drafting: a good solicitor should assess (and ideally document) the client's capacity at the time of giving instructions and again at signing. When that documentation exists and shows the person understood what they were doing, it becomes very difficult to challenge the will on capacity grounds alone.
However — and this is where Vail is instructive — the court also recognized that two things together can shift the picture significantly:
- Evidence of cognitive decline around the time of signing (medical records, family observations, behaviour changes)
- A suspicious will that benefits a care provider or a recently arrived new partner, especially when it departs sharply from an earlier estate plan
When those two factors combine, courts have been willing to order a full trial to examine the question properly. The new beneficiary — whoever is trying to uphold the will — may then bear the burden of proving the will is valid.
What Evidence Actually Matters
If you're considering a challenge, you need to build a picture of your parent's cognitive state in the weeks and months surrounding the signing. Useful evidence includes:
Medical Records
Doctor's notes, specialist assessments, hospital records, and any formal cognitive testing (like a Montreal Cognitive Assessment) from around that period. A diagnosis of moderate-to-severe dementia documented shortly before the signing date carries significant weight.
Witness Observations
Statements from family members, neighbours, or friends who regularly interacted with your parent. Courts want specifics — not "she seemed confused" but "she asked me three times in one afternoon what month it was" or "he didn't recognize his own son when he visited in October."
The Circumstances of the Signing
Who arranged the appointment with the lawyer? Who drove your parent there? Was the lawyer given any background about the cognitive decline? Did anyone object at the time? If the will was arranged and accompanied entirely by the new beneficiary, that raises a red flag courts take seriously.
The Will Itself
A dramatic departure from a long-standing estate plan — especially one that benefits a recent caregiver or romantic partner — is itself a piece of evidence. It doesn't prove incapacity, but it prompts harder scrutiny of the process.
When Undue Influence Is Also in Play
Capacity and undue influence are separate legal grounds, but they often appear together in the same case. If your parent had the cognitive ability to make a will (capacity), but was manipulated or pressured into signing one that doesn't reflect their real wishes (undue influence), that's a different — but equally valid — challenge.
Signs of undue influence include a caregiver or new partner who controlled access to your parent, isolated them from family, was present at the lawyer's appointment, or who had taken over financial management. If any of this sounds familiar, read our guide on undue influence will challenges in BC for more on what that claim requires.
The Time Limit to Act
In BC, you generally have two years from the date you knew — or reasonably should have known — about the will to bring a court challenge. Don't wait. Evidence fades, witnesses' memories dim, and medical records can become harder to obtain. If you suspect a problem, get legal advice early.
Under the Wills, Estates and Succession Act (WESA), you can also apply to the court to require disclosure of the will and the estate's assets while the estate is being administered, which is often a necessary first step before launching a formal challenge.
Is a Challenge Worth Pursuing?
Honestly? It depends. Capacity cases are not cheap to run, and outcomes are never guaranteed. Courts give weight to the presumption that a signed will is valid, so the burden falls on the person challenging it to produce clear evidence.
But if you have credible medical evidence of significant cognitive decline, a will that looks like it was engineered by someone who stood to benefit, and a pattern of isolation or control — there may be a strong case worth pursuing.
The first step is a frank conversation with a lawyer who knows BC estate litigation. Book a consultation with Nanuq Law to talk through what you have and what it would take to challenge the will.
Frequently Asked Questions
Does a dementia diagnosis automatically void a will in BC?
No. A diagnosis of dementia — even one that predates the will — does not automatically mean the will is invalid. BC courts assess whether the person had testamentary capacity at the specific time they signed the will. Someone with early dementia may still meet the legal test if they understood what they were signing, what they owned, and who their family members were.
What is testamentary capacity in BC?
Testamentary capacity is the mental ability required to make a valid will. Under BC law, a person must understand: (1) that they are making a will and what that means; (2) the general extent of their property; (3) the family members or others who might have a claim on their estate; and (4) how these elements fit together into a coherent plan. This test comes from Banks v. Goodfellow (1870) and is consistently applied by BC courts.
How do I prove my parent lacked capacity when they signed their will?
You need evidence of their cognitive state around the time of signing — typically medical records, clinical assessments, and testimony from people who observed them regularly. A formal cognitive diagnosis combined with a will that suddenly benefits a new partner or caregiver is the kind of evidence that can persuade a court to order a full trial.
How long do I have to challenge a will in BC?
Generally, two years from the date you knew (or reasonably should have known) about the will and the grounds for challenging it. Because evidence and witness memory deteriorate over time, it's important to seek legal advice as soon as you have concerns.
What if both lack of capacity and undue influence apply?
Both can be pleaded in the same claim and often are. Lack of capacity and undue influence are separate legal grounds — you don't need to prove both, but if the facts support both arguments, a court will consider each. A lawyer can help you assess which grounds are strongest given your evidence.
Frequently Asked Questions
Does a dementia diagnosis automatically void a will in BC?
No. A diagnosis of dementia does not automatically invalidate a will in BC. Courts assess whether the person had testamentary capacity at the specific time they signed the will. Someone with early dementia may still meet the legal test if they understood what they were signing, what they owned, and who their family members were.
What is testamentary capacity in BC?
Testamentary capacity is the mental ability required to make a valid will. Under BC law, a person must understand: (1) that they are making a will and what that means; (2) the general extent of their property; (3) the family members or others who might have a claim on their estate; and (4) how these elements fit together into a coherent plan. This test comes from Banks v. Goodfellow (1870) and is consistently applied by BC courts.
How do I prove my parent lacked capacity when they signed their will in BC?
You need evidence of your parent's cognitive state around the time of signing — typically medical records, clinical assessments, and testimony from people who observed them regularly. A formal cognitive diagnosis combined with a will that suddenly benefits a new partner or caregiver can be enough to trigger a full trial.
How long do I have to challenge a will in BC?
Generally, you have two years from the date you knew — or reasonably should have known — about the will and the grounds for your challenge. Because evidence fades over time, it is important to seek legal advice as soon as you have concerns.
Can I challenge a will on both lack of capacity and undue influence in BC?
Yes. Both grounds can be pleaded in the same claim and often are. Lack of capacity and undue influence are separate legal arguments — you don't need to prove both, but if the facts support both, a court will consider each. A BC estate litigation lawyer can help you assess which grounds are strongest given your evidence.
