Lack of Testamentary Capacity in California: What the Law Requires

California tests will capacity by what the person could understand on the day they signed. They had to understand they were making a will. They had to have a general sense of what they owned and who their family was. They also could not be acting on a delusion that shaped the gifts. A diagnosis alone does not answer that question.

Most people facing this question are carrying something specific. Often it is a parent's will signed during an illness, a late change that left out a child or sibling, or a document that does not sound like the person they knew. Some readers are on the other side. They are named in a will and are now hearing that the person who signed it "wasn't all there." Either way, the reader is trying to work out whether doubts about a loved one's mind add up to a legal challenge that a California probate court would hear.

This article explains the statute that sets the standard. It covers how each part of the test works, why the date of signing controls, who has to prove what, how a contest moves through court, and where capacity fits among the other grounds for challenging a will. In plain terms, testamentary capacity is the minimum mental ability the law requires for a person to make a valid will.

What Testamentary Capacity Means Under California Law

Probate Code section 6100.5 controls. It says a person is not mentally competent to make a will if, at the time of making the will, either of two things is true. The first is that the person lacked the mental capacity to do any one of three things. The second is that a mental health disorder with delusions or hallucinations shaped how the person left their property. You can read the text of section 6100.5 on the Legislature's site.

Read as a checklist, the statute produces four elements. At signing, the testator (the person making the will) had to be able to:

1. "Understand the nature of the testamentary act." The testamentary act is the act of making a will, meaning a document that decides who receives the person's property after death.
2. "Understand and recollect the nature and situation of the individual's property."
3. "Remember and understand the individual's relations to living descendants, spouse, and parents, and those whose interests are affected by the will."
4. Not be suffering from "a mental health disorder with symptoms including delusions or hallucinations, which delusions or hallucinations result in the individual's devising property in a way that, except for the existence of the delusions or hallucinations, the individual would not have done."

The first three elements are separate requirements. Lacking the ability to do any one of them is enough to show incapacity. The fourth is a separate route to the same result.

Each element asks about understanding. None asks about sharpness, memory for daily details, or good judgment. That makes the threshold relatively modest. A person with real cognitive decline can still meet all four elements. Probate Code section 810(b) says so directly: a person with a mental or physical disorder "may still be capable of... executing wills or trusts." A dementia or Alzheimer's diagnosis, standing alone, does not make a will invalid.

The Four Elements in Practice: What Each One Requires

Picture the moment the pen touches the page. Each element asks a different question about what was going on in the testator's mind at that moment.

Understanding the testamentary act. The testator needed to know they were signing a document that gives away their property at death. A person who believed they were signing a lease, a medical form, or a birthday card would not meet this element.

Understanding and recollecting property. The statute does not require an inventory or exact values. The question is whether the person had a general awareness of what they owned, such as the house, the accounts, or the business, and of its general situation.

Remembering and understanding family relations. This element looks at whether the testator could identify their children, spouse and parents, and the others whose interests the will affects, and could understand how the will treats them. Disinheritance disputes often turn on this element. Nothing in § 6100.5 requires a will to treat family members equally or fairly. A testator who meets the test and acts freely may leave out a sibling, a child or anyone else. The legal question is whether the person could remember and understand those relationships, not whether the result seems kind.

Delusions or hallucinations. Lawyers often call this an "insane delusion." In plain terms, it is a fixed false belief, rooted in a mental health disorder, that does not match reality. An example would be a belief that a devoted child is stealing from the household when nothing of the kind is happening. The statute requires a causal link. The delusion must have led the person to leave property in a way they otherwise would not have. A delusion that existed alongside the will, but had nothing to do with its gifts, does not satisfy this element.

Two distinctions matter here. Testamentary capacity is not the same as the capacity to sign a contract. Section 810(b) lists contracting and executing wills as separate acts, and section 810(c) ties any finding of incapacity to "a specific act." A person may have been able to do one and not the other. Testamentary capacity is also separate from undue influence. That ground is discussed briefly below and covered in more depth elsewhere on this site.

Capacity Is Tested at the Time the Will Was Signed

The date on the signature line is the date that matters. Section 6100.5 asks about the testator's mind "at the time of making the will." It does not ask about the date of death, the date of a diagnosis, or the testator's general condition over the final years.

This rule works in both directions. Some people have good days and bad days. A will signed during a lucid interval, meaning a period of clear thinking, may be valid even if the person was often impaired before and after. On the other hand, a person who seemed fine at a family dinner may still have lacked capacity at the specific time of signing.

Because the focus is so narrow, the most useful evidence tends to come from close to the signing date. That evidence typically includes:

• Medical and care records from the days or weeks around the signing
• What the witnesses saw and heard during the signing
• Notes kept by the attorney who supervised the signing
• Video or audio recordings of the signing, if any exist

Who carries the burden of proving the testator's state of mind is a separate question. The next section addresses it.

Burden of Proof in a Capacity Challenge

Probate Code section 8252(a) assigns the burden. The people defending the will must prove "due execution," meaning the will was properly signed and witnessed. The contestants (the people challenging the will) carry "the burden of proof of lack of testamentary intent or capacity, undue influence, fraud, duress, mistake, or revocation." The court then decides "any contested issue of fact that affects the validity of the will" (section 8252(b)).

Section 810(a) adds a related rule. It creates a rebuttable presumption that "all persons have the capacity to make decisions and to be responsible for their acts or decisions." A rebuttable presumption is a starting assumption that holds unless evidence overcomes it. In practice, the person challenging a will for incapacity begins at a disadvantage and has to bring proof.

The proof usually comes from several sources considered together:

• Testimony from people who saw the testator's behavior, such as family members, friends, caregivers and neighbors
• Medical records
• Testimony from physicians or neuropsychologists, sometimes based on a review of records after death
• The will itself: whether it reads coherently and matches the testator's known circumstances

For a family that watched a loved one decline, it can feel as though the decline should speak for itself. The court's question is narrower than that. It asks what the evidence shows about the testator's understanding on one specific day.

This burden is different from the presumption under Probate Code section 21380, which is discussed in the final section. That presumption shifts the burden for certain gifts and belongs to a separate doctrine.

How a Will Contest for Lack of Capacity Proceeds in California

When the will has not yet been admitted to probate, the contest begins with a filing. Under Probate Code section 8250(a), the contestant files "an objection to probate of the will." A summons is then issued and served, along with a copy of the objection, on the people entitled to notice of the petition for administration. The summons directs the people served to "file with the court a written pleading in response to the contest within 30 days after service of the summons." Under section 8250(b), a person named as executor has no duty to defend the contest until appointed personal representative.

After the will has been admitted, a different path applies. Under Probate Code section 8270(a), any interested person may petition to revoke the probate of the will within 120 days after the will is admitted to probate. Two groups are excluded: a person who was a party to a will contest, and a person who had actual notice of a will contest in time to join it. The petition must include written objections stating the grounds. Section 8270(b) contains an exception. A person who was a minor, or who was incompetent and had no guardian or conservator, when the will was admitted may petition at any time before the order for final distribution is entered. The 120 days run from admission to probate, not from the date of death.

These cases are heard in the Superior Court of California for the county where the estate is pending. The California Courts website publishes general information about probate proceedings. Challenges to a trust, rather than a will, follow their own rules. That process is explained in the guide on how to contest a trust.

Lack of capacity is only one ground for a contest. Improper execution, meaning a failure to meet the formal signing requirements, is a separate ground. As noted above, the people defending the will must prove proper execution.

What a Diagnosis Does — and Does Not — Establish

Medical labels carry a lot of weight in families, and in court they carry less than people expect. A diagnosis of dementia, Alzheimer's disease or another cognitive condition is not, by itself, proof that a will fails § 6100.5. Section 810(c) says that a finding of incapacity "should be based on evidence of a deficit in one or more of the person's mental functions rather than on a diagnosis of a person's mental or physical disorder."

A diagnosis is still relevant evidence. It can support an argument that the testator's understanding was impaired when the will was signed, particularly when records describe what the person could and could not do. The legal question, however, remains the four elements at the time of signing.

Timing affects how much a diagnosis is worth. A diagnosis made months or years after the signing does not, on its own, show incapacity on the signing date. Records made close to the signing that describe orientation, memory and recognition of family usually say more than a later diagnosis code.

General cognitive decline is also different from the delusion element. A delusion under § 6100.5(a)(2) is a specific false belief that caused a specific gift. Forgetfulness, confusion or slowed thinking may support a challenge under the first three elements. Those symptoms do not satisfy the delusion element.

Testamentary Capacity and Related Grounds for Contesting a Will

Capacity is one of several grounds the law recognizes. Section 8252(a) lists it alongside lack of testamentary intent, undue influence, fraud, duress, mistake and revocation. Contests frequently raise more than one ground.

Undue influence. Probate Code section 86 gives "undue influence" the meaning defined in the Welfare and Institutions Code, and it supplements the common law meaning of the term. Undue influence is a separate ground from incapacity. A testator who fully met § 6100.5 can still have made a will that a court finds was the product of undue influence.

The section 21380 presumption. Under Probate Code section 21380(a), a gift in an instrument is presumed to be the product of fraud or undue influence when it goes to certain people. These include the person who drafted the instrument; a person in a fiduciary relationship with the transferor who transcribed it or caused it to be transcribed; and a care custodian of a dependent adult, if the instrument was signed while the care custodian was providing services or within 90 days before or after that period. Certain relatives, cohabitants, employees and law-firm associates of those people are also covered. The list is partial. The presumption affects the burden of proof. Under section 21380(b), it can be rebutted by "clear and convincing evidence," a higher standard than ordinary proof. For gifts to the drafter and to the people section 21380(c) associates with the drafter, the presumption is conclusive and cannot be rebutted. Under section 21380(d), a beneficiary who fails to rebut it bears all costs of the proceeding, including reasonable attorney's fees. Not every gift to a caregiver or relative is presumed invalid. The presumption applies only to the people the statute describes.

Improper execution and fraud. A will that was not signed and witnessed as the law requires can be challenged on that basis. Fraud is another distinct ground.

No contest clauses. Some wills say that anyone who challenges them loses their gift. Under Probate Code section 21311(a), such a clause can be enforced only against the following:

• A direct contest brought without probable cause
• A challenge claiming property was not the transferor's at the time of transfer, and only if the clause expressly covers that type of challenge
• A creditor's claim or an action based on one, and only if the clause expressly covers that type of claim

Under section 21311(b), probable cause exists if, when the contest is filed, the known facts would cause a reasonable person to believe there is a reasonable likelihood the relief will be granted after an opportunity for further investigation or discovery. A no contest clause does not automatically disinherit everyone who challenges a will. The full range of fiduciary and estate disputes is described on the California trust litigation attorney page.

If You'd Like to Talk Through a Capacity Question

Capacity disputes usually turn on a short stretch of time and a small set of records. An attorney typically looks at the date the will was signed, the medical and care records from around that date, who was present at the signing, any earlier wills, and whether the will has already been admitted to probate. That last fact determines whether the § 8250 or § 8270 rules apply. This page is not written for anyone planning their own estate or handling an estate that nobody disputes. Those questions belong elsewhere.

To discuss a contested will with an attorney, contact California Trust Litigation Lawyers to request a consultation about your dispute.