Challenging a California Trust on Grounds of Incapacity or Undue Influence: What the Law Requires—and What It Takes to Prove
One of the most common attacks on a California trust is the claim that the trust—or a trust amendment—is invalid and cannot be enforced. Although invalidity may seem obvious to a challenger, these cases are often difficult to win because California law starts with strong presumptions: adults are presumed to have capacity, and undue influence must be proven with specific, legally recognized elements.
This article provides a clear, practical breakdown of the two most common trust‑contest theories under California law: incapacity and undue influence.
1. Incapacity (Lack of Mental Capacity)
A. California Presumes Capacity
California Probate Code § 810 creates a rebuttable presumption that all persons have the capacity to make decisions—even those with mental or physical disorders. Capacity is decision‑specific: a person may be competent to make some decisions but not others.
B. Two Key Legal Frameworks Used in Trust Contests
1. Testamentary Capacity — Probate Code § 6100.5
This standard, commonly applied to wills and some trust amendments, finds a person mentally incompetent if they cannot:
Understand the nature of the testamentary act,
Understand and recollect their property, or
Recall and understand their relationships to family and those affected by the document.
Capacity can also fail when delusions or hallucinations cause dispositions the person would not otherwise make.
2. Decision‑Making Capacity — Probate Code §§ 810–812
For trusts (especially complex ones), courts often rely on Probate Code §§ 810–812, which require:
Evidence of deficits in specific mental functions (memory, reasoning, disorganized thinking, etc.), and
A correlation between those deficits and the ability to execute the trust at issue.
A diagnosis alone is not enough—California requires evidence of functional impairment tied to the act itself.
C. How to Prove Incapacity
1. Witness Testimony
Strong cases use testimony from people who observed the settlor on or near the signing date:
Family and friends familiar with baseline cognition
Caregivers
Anyone present at execution
Their observations should describe concrete impairments: confusion about assets, inability to follow conversations, disorientation, or failure to recognize close family.
2. Medical and Institutional Records
Useful records include:
Cognitive assessments
Neurological and psychological evaluations
Repeated physician observations tied to functional deficits
These documents help establish whether mental‑function deficits existed near execution, not just in general.
3. Expert Testimony
Experts such as neurologists, psychiatrists, or neuropsychologists can synthesize records and testimony to explain how specific deficits impaired decision-making.
4. Lucid Intervals
For persons with fluctuating cognition, courts presume a document was executed during a lucid period unless evidence shows otherwise. Thus, timing is everything: challengers must present evidence from the critical window.
2. Undue Influence
A. California’s Modern Definition
California Probate Code § 86 incorporates the statutory definition of undue influence from Welfare & Institutions Code § 15610.70. Under that statute, undue influence is:
“Excessive persuasion that overcomes a person’s free will and results in inequity.”
Courts must evaluate four categories:
1. Vulnerability of the Victim
Evidence includes illness, cognitive impairment, isolation, emotional distress, dependency, and whether the influencer knew or should have known of the vulnerability.
2. Influencer’s Apparent Authority
Examples: fiduciaries, caregivers, family members, professionals, spiritual advisers.
3. Actions or Tactics Used
This is often the heart of the case and includes:
Isolation from family
Controlling medication or necessities
Use of affection, intimidation, or coercion
Secrecy, haste, or inappropriate timing/place of execution
Claiming special expertise
4. Equity of the Result
Courts look at:
Divergence from prior intent
Economic consequences
Disproportionate benefits to the influencer
Important: An unfair result alone is insufficient without evidence of undue influence tactics.
3. Presumptions That Strengthen Undue Influence Claims
A. Probate Code § 21380 — Presumption of Fraud or Undue Influence
California law presumes certain transfers are the product of fraud or undue influence when they benefit:
The drafter of the document
Someone who transcribed it while in a fiduciary role
Certain care custodians of dependent adults
People related to or associated with those individuals
This presumption shifts the burden to the beneficiary to prove, by clear and convincing evidence, that the transfer was not the product of undue influence. Some circumstances create a conclusive presumption that cannot be rebutted.
If the beneficiary fails to rebut the presumption, they may also be ordered to pay legal fees and costs.
4. What Successful Trust Contests Have in Common
A. Evidence Directly Tied to the Signing Date
Both incapacity and undue influence turn on conditions at the exact time the trust or amendment was executed.
B. A “Mosaic” of Proof
Winning cases usually combine:
Witness accounts
Medical evidence
Expert analysis
Communications showing isolation or coercion
Patterns showing deviation from long‑standing estate plans
C. Strategic Use of Statutory Presumptions
Section 21380 can dramatically change the case by shifting or conclusively resolving the burden of proof.
