Trusts · · Updated · 9 min read
Can You Contest a Will Because of Dementia in California?
Published by Corcoran Smith Law Corp..
California asks whether the person understood what they were doing when they signed, not whether they had a diagnosis. A will can stand despite documented dementia, and can fail on a day the person could not understand their property or their family. The evidence that decides it is contemporaneous and specific.
A dementia diagnosis does not by itself invalidate a California will. The law asks a narrower question: at the moment of signing, did the person understand what they were doing. That is why two people with similar diagnoses can produce different outcomes, and why the evidence that matters is nearly always about a particular day rather than about a condition.
What does capacity actually require?
The standard for a will is deliberately modest. The person must understand the nature of the act they are performing, have a general understanding of the property they own, and know the people who would ordinarily be expected to inherit from them. California also treats capacity as a matter of function rather than label, judged by identifiable deficits and their effect on the decision in question. The framework, and the sections behind it, are set out on lack of capacity.
Two consequences follow. A person can lack capacity to run their finances and still have capacity to sign a simple will. And a complicated instrument can demand more understanding than a simple one, which is why the same person may validly sign one document and not another.
Why is a diagnosis not enough?
Because a diagnosis describes a condition across time, and the contest is about a moment. Dementia fluctuates. Many people have hours of clarity, and a will signed in one of them can stand. Conversely, an undiagnosed person can lack capacity on the day.
That is also why the strongest evidence is rarely the medical conclusion. It is the record of what the person actually did and said around the signing: whether they knew what they owned, whether they could name the family members a will would ordinarily consider, whether they understood what the document was for.
California measures testamentary capacity at the moment the will was signed, not across the course of an illness. The person must understand the nature of the act, have a general understanding of the property they own, and recognize the people who would ordinarily inherit from them, and capacity is assessed through identifiable functional deficits and their connection to that decision rather than through a diagnosis alone. A will signed during a period of clarity can therefore be valid despite documented dementia, and a will signed on a day the person could not hold those facts in mind can fail even without one. Because the question is fixed to a date, contemporaneous evidence controls: clinical notes describing orientation and memory at the time, cognitive testing, the drafting lawyer's file, and the accounts of people who were present. A more demanding instrument can require more understanding than a simple one, which is why the same person may validly sign a straightforward will and not a complex trust amendment.
What evidence decides these cases?
| What the court asks | What answers it | Where it usually comes from |
|---|---|---|
| Did they understand the act? | The drafting lawyer's notes and process | The attorney's file, the engagement record |
| Did they know their property? | Statements, deeds, and how they described assets | Financial records, correspondence |
| Did they know their family? | Who they named, and whether they could account for them | Witnesses, the instrument itself, prior versions |
| Was the deficit connected to this decision? | Clinical findings near the date | Treating records, cognitive testing |
| Did anything change abruptly? | Comparison with earlier documents | The prior will or trust and its amendments |
A note on process: much of this evidence belongs to other people, and access comes through the proceeding rather than through asking. Gather what you lawfully hold, list what you believe exists and where, and let counsel pursue the rest.
How does capacity differ from undue influence?
Capacity asks what the person understood. Undue influence asks whether someone overbore their will. A person who understood everything can still have been pressured, and the same facts often support both claims: isolation, a new adviser, a sudden change late in life, a beneficiary who arranged the appointment and drove to it.
California also presumes fraud or undue influence for certain transfers, including gifts to the person who drafted the instrument and to some care custodians. That presumption, and the certificate of independent review that can defeat it, are explained on how to contest a living trust, and the general framework is on undue influence. Where money moved during life rather than at death, the companion claim is financial elder abuse.
Will or trust: which one are you challenging?
The difference changes both the standard and the clock.
A will is challenged in the probate proceeding, usually after it is offered for probate. What makes a will valid in the first place is on will requirements, the grounds and the process are on will contest, and the wider category sits on will litigation.
A trust or an amendment is challenged by petition, and the period for doing so is generally set in motion by the trustee's notification. The deadline rules are on trust contest deadlines and the process on how to contest a living trust. Trust disputes more broadly sit on trust litigation.
Before filing either one, check the instrument for a no-contest clause and read no-contest clauses, because the risk of a weak filing is different from the risk of a well-evidenced one.
What should you do first?
- Write down the signing date, and everything you know about that week.
- Collect what you lawfully have: correspondence, photographs with dates, your own contemporaneous notes.
- List the records you believe exist, and who holds them: the treating practice, the drafting lawyer, the bank, the care facility.
- Identify the witnesses, including anyone who drove the person to the appointment.
- Get advice on timing before you spend months gathering. The deadline does not wait for a complete file, and the pages above explain which clock applies.
Questions worth bringing to a lawyer
- What is the date of the instrument, and is there an earlier version?
- What changed between the versions, and who benefited?
- What was the person's condition in the weeks either side of the signing?
- Who arranged the drafting, and who was present?
- Has anyone been served with a notice that starts a deadline?
These cases turn on records that get harder to obtain with time, so early advice is usually cheaper than a longer investigation. We answer at (213) 695-7353 around the clock, or you can tell us what happened in writing. Nothing you say commits you to anything.
Sources
- California Probate Code — California Legislative Information
- Probate Self-Help Resources — California Courts
- Free Legal Information — State Bar of California
Common questions
Can I contest a will if my parent had dementia in California?
You can raise lack of capacity, but the diagnosis is a starting point rather than the answer. The question is what your parent understood at the moment of signing: the nature of the act, the property involved, and the people who would ordinarily inherit. Records that describe function on or near that date carry far more weight than a diagnosis alone.
What evidence proves lack of capacity in a California will contest?
Contemporaneous and specific evidence: clinical notes describing orientation and memory around the signing date, cognitive testing, the drafting lawyer's file and notes, witnesses who observed the signing, and financial records showing whether the person could still manage their own affairs. Generic later testimony that someone was confused rarely carries a case by itself.
Is capacity the same question as undue influence?
No, and the difference matters. Capacity asks what the person understood. Undue influence asks whether someone else overcame their free will, which can happen to a person who understood perfectly well. The two are often pleaded together because the same facts, such as isolation and a sudden change, support both.
Need help with legal fees?
We litigate select cases on contingency, with no upfront fees.
Costs are separate from the fee, and whether you are responsible for them is set out in the written agreement before you sign anything.
How contingency fees work in California
A contingency fee means the attorney is paid from what is recovered rather than by the hour, so a beneficiary who cannot fund litigation out of pocket can still bring a claim. California regulates these agreements closely. Under Business and Professions Code section 6147, the agreement must be in writing and the attorney must give the client a duplicate copy, signed by both, when the contract is made. It must state the agreed contingency rate; how disbursements and costs incurred in prosecuting or settling the claim will affect that fee; and to what extent the client could be required to pay for related matters. Unless the matter falls under section 6146, the agreement must also state that the fee is not set by law and is negotiable. These are not formalities: failure to comply with any provision of section 6147 makes the agreement voidable at the client’s option, leaving the attorney entitled only to a reasonable fee.
Sources: Business and Professions Code s.6147 - Contingency fee contracts · Verified 2026-08-03.
Not every matter suits a contingency arrangement, and the firm does not take every case on one. Whether yours qualifies depends on the facts, the likely recovery, and the assets actually available to satisfy a judgment. Ask when you call.
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