Mental Capacity and Wills: Can a Lack of Capacity Lead to a Disputed Will?
At Bochnewich Law Offices, we often hear from clients who are concerned about whether a loved one had the mental clarity to make a valid will. Questions about mental capacity can create serious disputes, especially when heirs feel the wishes expressed in the will don’t reflect the person’s true intent.
In California, mental capacity is a central issue in will contests. If someone lacked the legal capacity to make decisions at the time they signed their will, that document may not stand up in court.
That’s why we believe it’s critical to address mental capacity early in the estate planning process, particularly when working with older adults or those facing cognitive decline.
This article walks through how California law defines mental capacity for wills, how disputes arise, and what can be done to reduce the chances of a contested estate.
Testamentary Capacity According to California Law
In California, the law sets a relatively low threshold for someone to create a will. This is known as “testamentary capacity,” and it’s a specific standard distinct from broader definitions of mental competence.
According to California Probate Code Section 6100.5, a person must meet the following conditions to have the capacity to make a will:
Be at least 18 years old.
Understand the nature of making a will.
Know and understand the nature and extent of their property.
Recognize the people who are the natural objects of their bounty (such as children or close relatives).
Understand how their will disposes of their property.
In short, a person doesn’t need perfect memory or full mental sharpness. They just need to understand, in a general sense, what they’re doing and who stands to benefit from their decisions.
We’ve worked on many estate planning cases where clients had mild memory loss or early-stage dementia but still met this legal standard. What matters is their ability to comprehend the core elements of the will at the time it was signed.
How Mental Capacity Issues Lead to Will Disputes
Unfortunately, even when a will appears valid on its face, heirs or beneficiaries may challenge it if they believe the person lacked capacity. These disputes often surface after the person has passed away and surviving family members disagree about what the will says—or what it omits.
Challenges based on mental capacity often claim one of the following:
The person had dementia, Alzheimer’s disease, or another cognitive condition at the time the will was executed.
The person was under undue influence by a caregiver, child, or other party.
The person didn’t understand what they were signing.
The will contradicts earlier, consistent estate planning documents.
In these cases, the court may hear testimony from physicians, attorneys, caregivers, and family members to determine whether the person truly had the capacity to execute the will.
We’ve seen firsthand how these disputes can lead to drawn-out probate battles. That’s why, when we guide clients through the estate planning process, we take extra steps to document capacity and reduce the likelihood of future challenges.
Ways to Reduce the Risk of a Disputed Will
At Bochnewich Law Offices, we believe careful planning can prevent unnecessary legal battles. Here are several steps we recommend for minimizing the chance of a will being contested due to mental capacity:
Meet With an Attorney Early
Don’t wait until cognitive symptoms progress. If you or a loved one is beginning to show signs of memory loss, it's wise to begin estate planning while capacity is still clear.Use a Capacity Evaluation When Appropriate
In some cases, we suggest having a doctor evaluate and document mental capacity at the time of will execution. This can serve as strong evidence later.Include a Video or Written Statement
A brief video or signed letter explaining the person’s intent and understanding can go a long way in supporting the validity of the will.Avoid Sudden or Drastic Changes
Changing a long-standing estate plan to disinherit close family members or benefit a new acquaintance can raise red flags. If changes are needed, we advise documenting the reasoning clearly.Have Independent Witnesses Present
California requires two witnesses for a valid will, but selecting impartial people (who aren’t named in the will) adds further credibility.Work With an Experienced Attorney
A professionally drafted will—executed in a formal setting—carries more weight than something handwritten without legal guidance.Communicate with Family
When possible, let your family know about your estate planning choices in advance. Even brief conversations can reduce shock or confusion later.
These simple steps may not guarantee there won’t be a challenge, but they put you in a stronger legal position if one arises.
Undue Influence and Its Connection to Capacity
Another way mental capacity disputes surface is through claims of undue influence. In California, undue influence occurs when someone exerts excessive pressure on a person with diminished capacity, causing them to make decisions they wouldn’t have otherwise made.
Under California Welfare and Institutions Code Section 15610.70, courts evaluate whether undue influence existed by looking at several factors:
Vulnerability of the victim
Apparent authority of the influencer
Actions or tactics used
Resulting benefit to the influencer
If someone with declining mental function rewrites their will to benefit a caregiver, distant relative, or new acquaintance, courts will take a closer look. That’s why it’s so important to build a strong record showing that the will reflects true intent, not someone else's manipulation.
We’ve worked on both sides of these cases—defending valid wills and contesting suspicious ones. In each situation, the foundation is built on clear facts and consistent documentation.
What Happens If a Will Is Declared Invalid?
If a California court finds that someone lacked capacity at the time they created or changed their will, that will can be declared invalid. When that happens, one of two outcomes usually follows:
A previous valid will is reinstated (if one exists).
If there is no prior valid will, the estate passes according to California intestate succession laws.
Intestate succession distributes property to the closest relatives—starting with spouses and children, then moving outward to parents, siblings, and other kin. This result may not match the deceased person’s true wishes, especially if they had reasons for wanting a different distribution.
That’s why we tell every client: estate planning is about clarity. The more intentional and well-documented your plan is, the less likely it will be undone by court proceedings later.
Capacity Issues Beyond Wills
While this article focuses on wills, mental capacity also matters in other areas of estate planning, such as:
Powers of attorney
Revocable living trusts
Advance health care directives
Each of these documents requires different levels of capacity under California law. For example, creating a trust may require a higher understanding than making a will. That’s why we assess capacity carefully depending on the document and the client’s condition at the time.
In our experience, families often avoid significant hardship when these tools are put in place early—while capacity is not in question. These documents can also provide backup plans in case someone becomes incapacitated later.
How We Approach Estate Planning With Capacity in Mind
At Bochnewich Law Offices, we don’t just draft documents. We work with clients to create estate planning strategies that reflect their wishes and withstand legal scrutiny. That includes careful attention to capacity from the very first meeting.
When capacity is in question, we may schedule more frequent meetings, take detailed notes, bring in medical professionals, or recommend other protective measures. These efforts help make sure our client’s plan is honored and reduces the risk of litigation down the road.
We also assist clients and families dealing with the aftermath of disputed wills. Whether you're defending a valid estate plan or challenging a will made under questionable circumstances, we apply California property and estate laws to build your strongest case.
Clarity Now Prevents Conflict Later
At Bochnewich Law Offices, we help clients address these concerns head-on. We’re proud to serve Southern California, including Riverside County, Los Angeles County, San Bernardino County, Orange County, and San Diego County. Call today.