Your parent changed their will or trust just before they passed. A person they barely knew is suddenly the sole beneficiary. The estate you were told would support you is gone, rerouted by documents no one showed you until it was too late. And the version of your loved one who signed that will? That wasn’t the person you knew.
Something is wrong.
Under California law, you can challenge a will or trust based on a lack of testamentary capacity. If your loved one didn’t have the mental ability to understand what they were signing, the document may not be valid. But suspicion alone isn’t enough. You need clear, admissible evidence and a legal strategy tailored to your specific case facts.
At Geremia & Cullen, PC, we provide practical insight and advice to families during emotionally charged capacity contests. We don’t just handle the legal side; we help you navigate the grief, conflict, and confusion that often accompany these claims.
What Is Considered a Lack of Testamentary Capacity?
In California, the standard for testamentary capacity is relatively low, but it is not without limits. Under California Probate laws, a person cannot make a will if they do not understand:
- What a will or trust is and what it does,
- The nature and extent of their assets, and
- Who would naturally inherit (including children, spouse, siblings, and descendants).
For example, although someone is diagnosed with dementia or mental illness, if they understand those three things at the time they sign, they may not lack testamentary capacity and can still legally execute a will. However, if they couldn’t understand the document’s purpose or recognize close family members, the will or trust may be invalid. This type of situation is where the legal fight often begins.
How to Prove Mental Incapacity in California Estate Litigation
Here’s how to prove mental incapacity in a California will or trust contest:
Medical Records
These are your strongest evidence. Documentation of dementia, Alzheimer’s, stroke, psychosis, or other cognitive disorders from around the time of the document’s execution can help establish incapacity. Records from primary care physicians, neurologists, and hospitals carry significant weight.
Witness Testimony
Friends, family, caregivers, and neighbors who interacted with your loved one before they signed the document may offer insight into their mental state. Were they confused about time or place? Did they forget names or events? These anecdotes can support a broader picture.
Expert Evaluations
A forensic psychiatrist or neuropsychologist can review medical records and offer a professional opinion on whether the testator had the mental capacity required by law. Courts often give this type of testimony substantial credibility.
Video or Written Communication
Emails, texts, voicemails, and even social media posts may show patterns of confusion, paranoia, or detachment from reality.
Timing and Circumstances
Was the will executed while the person was in the hospital? Did a new beneficiary suddenly appear? Was a longtime estate plan changed abruptly? Suspicious timing can bolster your argument.
When proving mental incapacity, consistency matters. The goal is to show that, during signing, your loved one was not capable of understanding what they were doing, no matter how carefully someone may have guided their hand.
Capacity vs. Undue Influence: Know the Difference
Mental incapacity and undue influence often go hand in hand, but legally, they’re distinct claims. A person might technically have the capacity to sign a will but still be pressured or manipulated into doing something they wouldn’t have chosen otherwise. That’s undue influence, and California law treats it as a distinct legal reason to challenge a will or trust.
Capacity is about ability. Influence is about pressure. Sometimes, both may be relevant. At Geremia & Cullen, we’ll help you assess whether one or both legal theories support your claim.
Protect your loved one's true wishes.
We combine legal strategy with emotional understanding to help you challenge an estate plan that doesn’t reflect your loved one’s intent.
Common Scenarios Where Testamentary Capacity Is in Doubt
You may suspect a lack of testamentary capacity in situations where:
- An elderly parent dramatically alters their estate plan near the end of life;
- A person diagnosed with dementia signs a new trust;
- A caregiver becomes the sole heir after isolating the testator;
- Someone with a financial interest in the outcome drafts the will; or
- A previously consistent estate plan suddenly favors one child over others.
Confusion, grief, and conflict often mark these moments. That’s why it helps to work with a firm like Geremia & Cullen, which understands not only the law but also how it affects the people involved.
What Happens If You Win a Capacity Challenge?
If the court finds that your loved one lacked capacity when they signed the will or trust, the document may be declared invalid. In that case, an earlier valid will or trust, if one exists, may take effect.
Otherwise, the estate distribution will follow California’s intestacy laws. The intestacy process can result in a more equitable distribution among heirs and ensure that someone else’s manipulation doesn’t shape the outcome.
Why Does Timing Matter in Capacity Disputes?
California has strict deadlines for contesting a will or trust. A will contest must generally be filed before the will is admitted to probate. Once the court admits the will to probate, you typically have only 120 days to file a challenge.
For trusts, the timeline may depend on when you received notice of the trust and whether the trustee complied with notice requirements under California’s Trust Administration laws. Waiting too long can mean losing your right to bring a challenge, regardless of how valid your concerns may be.
How Can Geremia & Cullen, PC Help Me?
At Geremia & Cullen, PC, we bring decades of combined experience in trust and estate litigation. Attorney Brian Geremia has built a career representing disinherited heirs and vulnerable beneficiaries with precision and respect.
Attorney Sarah Cullen brings a lifetime of roots in the Sacramento community and a commitment to legal integrity to every case she handles. Together, they’ve earned nearly 40 five-star reviews and multiple industry recognitions—not by making empty promises but by offering honest guidance and consistently following through.
If you’re grappling with the possibility that a loved one didn’t know what they were signing, don’t wait in silence. We can help you clarify your legal options, review the facts, and take appropriate action when the evidence supports it.
Whether you’re just beginning to ask questions or are ready to take action, our team will walk you through your options and work to ensure your loved one’s true intentions are honored.
Contact Geremia & Cullen, PC, today to schedule a confidential consultation.
Resources:
- Trust administration notice requirements, Cal. Prob. Code §16061.7, link.
